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is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Ku%2C+H&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Ku%2C+H&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Ku%2C+H&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.17457">arXiv:2411.17457</a> <span> [<a href="https://arxiv.org/pdf/2411.17457">pdf</a>, <a href="https://arxiv.org/format/2411.17457">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Robustness of tripartite entangled states in passive PT-symmetric qubits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Feyisa%2C+C+G">C. G. Feyisa</a>, <a href="/search/quant-ph?searchtype=author&query=Liu%2C+C">Cheng-Yu Liu</a>, <a href="/search/quant-ph?searchtype=author&query=Hasan%2C+M+S">Muhammad S. Hasan</a>, <a href="/search/quant-ph?searchtype=author&query=You%2C+J+S">J. S. You</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Jen%2C+H+H">H. H. Jen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.17457v2-abstract-short" style="display: inline;"> Non-Hermitian quantum systems have attracted significant interest in recent years due to the presence of unique spectral singularities known as exceptional points (EPs), where eigenvalues and eigenvectors coalesce. The drastic changes in these systems around their EPs have led to unique entanglement dynamics, which remained elusive until quite recently. In this work, we theoretically investigate t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.17457v2-abstract-full').style.display = 'inline'; document.getElementById('2411.17457v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.17457v2-abstract-full" style="display: none;"> Non-Hermitian quantum systems have attracted significant interest in recent years due to the presence of unique spectral singularities known as exceptional points (EPs), where eigenvalues and eigenvectors coalesce. The drastic changes in these systems around their EPs have led to unique entanglement dynamics, which remained elusive until quite recently. In this work, we theoretically investigate the robustness of tripartite entanglement induced by EPs of the passive PT-symmetric non-Hermitian superconducting qubits, both in stand-alone configurations and hybrid setups with Hermitian qubits. In particular, we consider the qubits with both all-to-all and nearest-neighbour couplings under uniform and non-uniform coupling strengths. Our results reveal that non-Hermitian qubits with all-to-all coupling generate GHZ states, while those with nearest-neighbour interactions produce W states. These entangled states are resilient to non-uniform couplings and off-resonant driving fields. Moreover, the hybrid configurations combining Hermitian and non-Hermitian qubits suggest the importance of EPs for generating and maintaining genuine tripartite entanglement in our system. Additionally, driving the PT-symmetric qubits with a strong Rabi frequency can help sustain tripartite entanglement over time by countering losses, while strong inter-qubit coupling can benefit these entangled states in the low dissipation regime. These findings suggest that exploiting non-Hermitian systems and their associated EPs can create robust entangled states which are useful for both fundamental studies and quantum technologies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.17457v2-abstract-full').style.display = 'none'; document.getElementById('2411.17457v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.04430">arXiv:2410.04430</a> <span> [<a href="https://arxiv.org/pdf/2410.04430">pdf</a>, <a href="https://arxiv.org/format/2410.04430">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> The aspect of bipartite coherence in quantum discord to semi-device-independent nonlocality and its implication for quantum information processing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Jebarathinam%2C+C">Chellasamy Jebarathinam</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Cheng%2C+H">Hao-Chung Cheng</a>, <a href="/search/quant-ph?searchtype=author&query=Goan%2C+H">Hsi-Sheng Goan</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.04430v3-abstract-short" style="display: inline;"> Quantum discord can demonstrate quantum nonlocality in the context of a semi-device-independent Bell or steering scenario, i.e., by assuming only the Hilbert-space dimension. This work addresses which aspect of bipartite coherence is essential to such semi-device-independent quantum information tasks going beyond standard Bell nonlocality or quantum steering. It has been shown that the global cohe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.04430v3-abstract-full').style.display = 'inline'; document.getElementById('2410.04430v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.04430v3-abstract-full" style="display: none;"> Quantum discord can demonstrate quantum nonlocality in the context of a semi-device-independent Bell or steering scenario, i.e., by assuming only the Hilbert-space dimension. This work addresses which aspect of bipartite coherence is essential to such semi-device-independent quantum information tasks going beyond standard Bell nonlocality or quantum steering. It has been shown that the global coherence of a single system can be transformed into bipartite entanglement. However, global coherence can also be present in quantum discord. At the same time, discord can display bipartite coherence locally, i.e., only in a subsystem or both subsystems. Thus, global coherence of bipartite separable states is defined here as a form of bipartite coherence that is not reducible to local coherence in any of the subsystems or both subsystems. To answer the above-mentioned question, we demonstrate that global coherence is necessary to demonstrate semi-device-independent nonlocality of quantum discord in Bell or steering scenarios. From this result, it follows that any local operations of the form $桅_A \otimes 桅_B$ that may create coherence locally are free operations in the resource theory of semi-device-independent nonlocality of discord. As a byproduct, we identify the precise quantum resource for the quantum communication task of remote state preparation using two-qubit separable states. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.04430v3-abstract-full').style.display = 'none'; document.getElementById('2410.04430v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 4 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2409.03414">arXiv:2409.03414</a> <span> [<a href="https://arxiv.org/pdf/2409.03414">pdf</a>, <a href="https://arxiv.org/format/2409.03414">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Accelerating multipartite entanglement generation in non-Hermitian superconducting qubits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Feyisa%2C+C+G">Chimdessa Gashu Feyisa</a>, <a href="/search/quant-ph?searchtype=author&query=You%2C+J+S">J. S. You</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Jen%2C+H+H">H. H. Jen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2409.03414v1-abstract-short" style="display: inline;"> Open quantum systems are susceptible to losses in information, energy, and particles due to their surrounding environment. One novel strategy to mitigate these losses is to transform them into advantages for quantum technologies through tailored non-Hermitian quantum systems. In this work, we theoretically propose a fast generation of multipartite entanglement in non-Hermitian qubits. Our findings… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.03414v1-abstract-full').style.display = 'inline'; document.getElementById('2409.03414v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2409.03414v1-abstract-full" style="display: none;"> Open quantum systems are susceptible to losses in information, energy, and particles due to their surrounding environment. One novel strategy to mitigate these losses is to transform them into advantages for quantum technologies through tailored non-Hermitian quantum systems. In this work, we theoretically propose a fast generation of multipartite entanglement in non-Hermitian qubits. Our findings reveal that weakly coupled non-Hermitian qubits can accelerate multiparty entanglement generation by thousands of times compared to Hermitian qubits, in particular when approaching the $2^n$-th order exceptional points of $n$ qubits in the ${\cal P}{\cal T}-$ symmetric regime. Furthermore, we show that Hermitian qubits can generate GHZ states with a high fidelity more than $0.9995$ in a timescale comparable to that of non-Hermitian qubits, but at the expense of intense driving and large coupling constant. Our approach is scalable to a large number of qubits, presenting a promising pathway for advancing quantum technologies through the non-Hermiticity and higher-order exceptional points in many-body quantum systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.03414v1-abstract-full').style.display = 'none'; document.getElementById('2409.03414v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.06315">arXiv:2408.06315</a> <span> [<a href="https://arxiv.org/pdf/2408.06315">pdf</a>, <a href="https://arxiv.org/format/2408.06315">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Dynamical resource theory of incompatibility preservability </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Hsieh%2C+C">Chung-Yun Hsieh</a>, <a href="/search/quant-ph?searchtype=author&query=Stratton%2C+B">Benjamin Stratton</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+C">Chao-Hsien Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2408.06315v1-abstract-short" style="display: inline;"> The uncertainty principle is one of quantum theory's most foundational features. It underpins a quantum phenomenon called measurement incompatibility -- two physical observables of a single quantum system may not always be measured simultaneously. Apart from being fundamentally important, measurement incompatibility is also a powerful resource in the broad quantum science and technologies, with wi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.06315v1-abstract-full').style.display = 'inline'; document.getElementById('2408.06315v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.06315v1-abstract-full" style="display: none;"> The uncertainty principle is one of quantum theory's most foundational features. It underpins a quantum phenomenon called measurement incompatibility -- two physical observables of a single quantum system may not always be measured simultaneously. Apart from being fundamentally important, measurement incompatibility is also a powerful resource in the broad quantum science and technologies, with wide applications to cryptography, communication, random number generation, and device-independent tasks. Since every physical system is unavoidably subject to noise, an important, yet still open, question is how to characterise the ability of noisy quantum dynamics to preserve measurement incompatibility. This work fills this gap by providing the first resource theory of this ability, termed incompatibility preservability. We quantify incompatibility preservability by a robustness measure. Then, we introduce an operational task, entanglement-assisted filter game, to completely characterise both the robustness measure and the conversion of incompatibility preservability. Our results provide a general framework to describe how noisy dynamics affect the uncertainty principle's signature. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.06315v1-abstract-full').style.display = 'none'; document.getElementById('2408.06315v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4+5 pages; 4 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.14553">arXiv:2407.14553</a> <span> [<a href="https://arxiv.org/pdf/2407.14553">pdf</a>, <a href="https://arxiv.org/format/2407.14553">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Computational Physics">physics.comp-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Machine Learning for Improved Current Density Reconstruction from 2D Vector Magnetic Images </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Reed%2C+N+R">Niko R. Reed</a>, <a href="/search/quant-ph?searchtype=author&query=Bhutto%2C+D">Danyal Bhutto</a>, <a href="/search/quant-ph?searchtype=author&query=Turner%2C+M+J">Matthew J. Turner</a>, <a href="/search/quant-ph?searchtype=author&query=Daly%2C+D+M">Declan M. Daly</a>, <a href="/search/quant-ph?searchtype=author&query=Oliver%2C+S+M">Sean M. Oliver</a>, <a href="/search/quant-ph?searchtype=author&query=Tang%2C+J">Jiashen Tang</a>, <a href="/search/quant-ph?searchtype=author&query=Olsson%2C+K+S">Kevin S. Olsson</a>, <a href="/search/quant-ph?searchtype=author&query=Langellier%2C+N">Nicholas Langellier</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+M+J+H">Mark J. H. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Rosen%2C+M+S">Matthew S. Rosen</a>, <a href="/search/quant-ph?searchtype=author&query=Walsworth%2C+R+L">Ronald L. Walsworth</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.14553v2-abstract-short" style="display: inline;"> The reconstruction of electrical current densities from magnetic field measurements is an important technique with applications in materials science, circuit design, quality control, plasma physics, and biology. Analytic reconstruction methods exist for planar currents, but break down in the presence of high spatial frequency noise or large standoff distance, restricting the types of systems that… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.14553v2-abstract-full').style.display = 'inline'; document.getElementById('2407.14553v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.14553v2-abstract-full" style="display: none;"> The reconstruction of electrical current densities from magnetic field measurements is an important technique with applications in materials science, circuit design, quality control, plasma physics, and biology. Analytic reconstruction methods exist for planar currents, but break down in the presence of high spatial frequency noise or large standoff distance, restricting the types of systems that can be studied. Here, we demonstrate the use of a deep convolutional neural network for current density reconstruction from two-dimensional (2D) images of vector magnetic fields acquired by a quantum diamond microscope (QDM) utilizing a surface layer of Nitrogen Vacancy (NV) centers in diamond. Trained network performance significantly exceeds analytic reconstruction for data with high noise or large standoff distances. This machine learning technique can perform quality inversions on lower SNR data, reducing the data collection time by a factor of about 400 and permitting reconstructions of weaker and three-dimensional current sources. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.14553v2-abstract-full').style.display = 'none'; document.getElementById('2407.14553v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">17 pages, 10 figures. Includes Supplemental Information</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2403.10414">arXiv:2403.10414</a> <span> [<a href="https://arxiv.org/pdf/2403.10414">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Diamond Micro-Chip for Quantum Microscopy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Asif%2C+S">Shahidul Asif</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+H">Hang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Cremer%2C+J">Johannes Cremer</a>, <a href="/search/quant-ph?searchtype=author&query=Ravan%2C+S">Shantam Ravan</a>, <a href="/search/quant-ph?searchtype=author&query=Tamara-Isaza%2C+J">Jeyson Tamara-Isaza</a>, <a href="/search/quant-ph?searchtype=author&query=Lamsal%2C+S">Saurabh Lamsal</a>, <a href="/search/quant-ph?searchtype=author&query=Ebadi%2C+R">Reza Ebadi</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+Y">Yan Li</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+L">Ling-Jie Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Chang%2C+C">Cui-Zu Chang</a>, <a href="/search/quant-ph?searchtype=author&query=Xiao%2C+J+Q">John Q. Xiao</a>, <a href="/search/quant-ph?searchtype=author&query=Yacoby%2C+A">Amir Yacoby</a>, <a href="/search/quant-ph?searchtype=author&query=Walsworth%2C+R+L">Ronald L. Walsworth</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+M+J+H">Mark J. H. Ku</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2403.10414v1-abstract-short" style="display: inline;"> The nitrogen vacancy (NV) center in diamond is an increasingly popular quantum sensor for microscopy of electrical current, magnetization, and spins. However, efficient NV-sample integration with a robust, high-quality interface remains an outstanding challenge to realize scalable, high-throughput microscopy. In this work, we characterize a diamond micro-chip (DMC) containing a (111)-oriented NV e… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.10414v1-abstract-full').style.display = 'inline'; document.getElementById('2403.10414v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2403.10414v1-abstract-full" style="display: none;"> The nitrogen vacancy (NV) center in diamond is an increasingly popular quantum sensor for microscopy of electrical current, magnetization, and spins. However, efficient NV-sample integration with a robust, high-quality interface remains an outstanding challenge to realize scalable, high-throughput microscopy. In this work, we characterize a diamond micro-chip (DMC) containing a (111)-oriented NV ensemble; and demonstrate its utility for high-resolution quantum microscopy. We perform strain imaging of the DMC and find minimal detrimental strain variation across a field-of-view of tens of micrometer. We find good ensemble NV spin coherence and optical properties in the DMC, suitable for sensitive magnetometry. We then use the DMC to demonstrate wide-field microscopy of electrical current, and show that diffraction-limited quantum microscopy can be achieved. We also demonstrate the deterministic transfer of DMCs with multiple materials of interest for next-generation electronics and spintronics. Lastly, we develop a polymer-based technique for DMC placement. This work establishes the DMC's potential to expand the application of NV quantum microscopy in materials, device, geological, biomedical, and chemical sciences. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.10414v1-abstract-full').style.display = 'none'; document.getElementById('2403.10414v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Includes supplementary materials section</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.16789">arXiv:2402.16789</a> <span> [<a href="https://arxiv.org/pdf/2402.16789">pdf</a>, <a href="https://arxiv.org/format/2402.16789">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Entanglement-breaking channels are a quantum memory resource </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Vieira%2C+L+B">Lucas B. Vieira</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Budroni%2C+C">Costantino Budroni</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2402.16789v1-abstract-short" style="display: inline;"> Entanglement-breaking channels (equivalently, measure-and-prepare channels) are an important class of quantum operations noted for their ability to destroy multipartite spatial quantum correlations. Inspired by this property, they have also been employed in defining notions of "classical memory", under the assumption that such channels effectively act as a classical resource. We show that, in a si… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.16789v1-abstract-full').style.display = 'inline'; document.getElementById('2402.16789v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.16789v1-abstract-full" style="display: none;"> Entanglement-breaking channels (equivalently, measure-and-prepare channels) are an important class of quantum operations noted for their ability to destroy multipartite spatial quantum correlations. Inspired by this property, they have also been employed in defining notions of "classical memory", under the assumption that such channels effectively act as a classical resource. We show that, in a single-system multi-time scenario, entanglement-breaking channels are still a quantum memory resource: a qudit going through an entanglement-breaking channel cannot be simulated by a classical system of same dimension. We provide explicit examples of memory-based output generation tasks where entanglement-breaking channels outperform classical memories of the same size. Our results imply that entanglement-breaking channels cannot be generally employed to characterize classical memory effects in temporal scenarios without additional assumptions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.16789v1-abstract-full').style.display = 'none'; document.getElementById('2402.16789v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 3 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.06939">arXiv:2312.06939</a> <span> [<a href="https://arxiv.org/pdf/2312.06939">pdf</a>, <a href="https://arxiv.org/format/2312.06939">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Visually quantifying single-qubit quantum memory </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Chang%2C+W">Wan-Guan Chang</a>, <a href="/search/quant-ph?searchtype=author&query=Ju%2C+C">Chia-Yi Ju</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+G">Guang-Yin Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.06939v1-abstract-short" style="display: inline;"> To store quantum information, quantum memory plays a central intermediate ingredient in a network. The minimal criterion for a reliable quantum memory is the maintenance of the entangled state, which can be described by the non-entanglement-breaking (non-EB) channel. In this work, we show that all single-qubit quantum memory can be quantified without trusting input state generation. In other words… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.06939v1-abstract-full').style.display = 'inline'; document.getElementById('2312.06939v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.06939v1-abstract-full" style="display: none;"> To store quantum information, quantum memory plays a central intermediate ingredient in a network. The minimal criterion for a reliable quantum memory is the maintenance of the entangled state, which can be described by the non-entanglement-breaking (non-EB) channel. In this work, we show that all single-qubit quantum memory can be quantified without trusting input state generation. In other words, we provide a semi-device-independent approach to quantify all single-qubit quantum memory. More specifically, we apply the concept of the two-qubit quantum steering ellipsoids to a single-qubit quantum channel and define the channel ellipsoids. An ellipsoid can be constructed by visualizing finite output states within the Bloch sphere. Since the Choi-Jamio艂kowski state of a channel can all be reconstructed from geometric data of the channel ellipsoid, a reliable quantum memory can be detected. Finally, we visually quantify the single-qubit quantum memory by observing the volume of the channel ellipsoid. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.06939v1-abstract-full').style.display = 'none'; document.getElementById('2312.06939v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 5 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.01055">arXiv:2312.01055</a> <span> [<a href="https://arxiv.org/pdf/2312.01055">pdf</a>, <a href="https://arxiv.org/ps/2312.01055">ps</a>, <a href="https://arxiv.org/format/2312.01055">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Unveiling quantum steering by quantum-classical uncertainty complementarity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Lee%2C+K">Kuan-Yi Lee</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+J">Jhen-Dong Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Lemr%2C+K">Karel Lemr</a>, <a href="/search/quant-ph?searchtype=author&query=%C4%8Cernoch%2C+A">Anton铆n 膶ernoch</a>, <a href="/search/quant-ph?searchtype=author&query=Miranowicz%2C+A">Adam Miranowicz</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.01055v3-abstract-short" style="display: inline;"> One of the remarkable aspects of quantum steering is its ability to violate local uncertainty complementarity relations. In this vein of study, various steering witnesses employing different uncertainty relations have been developed including Reid's criteria. Here, we introduce a novel complementarity relation between system's quantum and classical uncertainties corresponding to the distillable co… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.01055v3-abstract-full').style.display = 'inline'; document.getElementById('2312.01055v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.01055v3-abstract-full" style="display: none;"> One of the remarkable aspects of quantum steering is its ability to violate local uncertainty complementarity relations. In this vein of study, various steering witnesses employing different uncertainty relations have been developed including Reid's criteria. Here, we introduce a novel complementarity relation between system's quantum and classical uncertainties corresponding to the distillable coherence and the von-Neumann entropy, respectively. We demonstrate a superior steering detection efficiency compared to an entropic uncertainty relation. Notably, our proposed steering witness can detect ``all pure entangled states," while the entropic uncertainty relation cannot. We also experimentally validate such a property through a photonic system. Furthermore, a deeper connection to the uncertainty principle is revealed by showcasing the functionality of our proposed complementarity as a quantifier of measurement incompatibility and quantum steerability under genuine incoherent operations. Our work establishes a clear quantitative and operational link between coherence and steering, which are significant resources of quantum technologies, and underscores our efforts in bridging the uncertainty principle with quantum coherence. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.01055v3-abstract-full').style.display = 'none'; document.getElementById('2312.01055v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages, 5 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.06191">arXiv:2309.06191</a> <span> [<a href="https://arxiv.org/pdf/2309.06191">pdf</a>, <a href="https://arxiv.org/format/2309.06191">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Characterisation and fundamental limitations of irreversible stochastic steering distillation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Hsieh%2C+C">Chung-Yun Hsieh</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Budroni%2C+C">Costantino Budroni</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.06191v1-abstract-short" style="display: inline;"> Steering resources, central for quantum advantages in one-sided device-independent quantum information tasks, can be enhanced via local filters. Recently, reversible steering conversion under local filters has been fully characterised. Here, we solve the problem in the irreversible scenario, which leads to a complete understanding of stochastic steering distillation. This result also provides an o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.06191v1-abstract-full').style.display = 'inline'; document.getElementById('2309.06191v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.06191v1-abstract-full" style="display: none;"> Steering resources, central for quantum advantages in one-sided device-independent quantum information tasks, can be enhanced via local filters. Recently, reversible steering conversion under local filters has been fully characterised. Here, we solve the problem in the irreversible scenario, which leads to a complete understanding of stochastic steering distillation. This result also provides an operational interpretation of the max-relative entropy as the optimal filter success probability. We further show that all steering measures can be used to quantify measurement incompatibility in certain stochastic steering distillation scenarios. Finally, for a broad class of steering robustness measures, we show that their maximally achievable values in stochastic steering distillation are always upper bounded by different types of incompatibility robustness measures. Hence, measurement incompatibility sets the fundamental limitations for stochastic steering distillation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.06191v1-abstract-full').style.display = 'none'; document.getElementById('2309.06191v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5+4 pages; 2 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.16040">arXiv:2308.16040</a> <span> [<a href="https://arxiv.org/pdf/2308.16040">pdf</a>, <a href="https://arxiv.org/format/2308.16040">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Native approach to controlled-Z gates in inductively coupled fluxonium qubits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ma%2C+X">Xizheng Ma</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+G">Gengyan Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+F">Feng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Bao%2C+F">Feng Bao</a>, <a href="/search/quant-ph?searchtype=author&query=Chang%2C+X">Xu Chang</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+J">Jianjun Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+H">Hao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Gao%2C+R">Ran Gao</a>, <a href="/search/quant-ph?searchtype=author&query=Gao%2C+X">Xun Gao</a>, <a href="/search/quant-ph?searchtype=author&query=Hu%2C+L">Lijuan Hu</a>, <a href="/search/quant-ph?searchtype=author&query=Ji%2C+H">Honghong Ji</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Lu%2C+K">Kannan Lu</a>, <a href="/search/quant-ph?searchtype=author&query=Ma%2C+L">Lu Ma</a>, <a href="/search/quant-ph?searchtype=author&query=Mao%2C+L">Liyong Mao</a>, <a href="/search/quant-ph?searchtype=author&query=Song%2C+Z">Zhijun Song</a>, <a href="/search/quant-ph?searchtype=author&query=Sun%2C+H">Hantao Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Tang%2C+C">Chengchun Tang</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+F">Fei Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+H">Hongcheng Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+T">Tenghui Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Xia%2C+T">Tian Xia</a>, <a href="/search/quant-ph?searchtype=author&query=Ying%2C+M">Make Ying</a>, <a href="/search/quant-ph?searchtype=author&query=Zhan%2C+H">Huijuan Zhan</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+T">Tao Zhou</a> , et al. (5 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.16040v1-abstract-short" style="display: inline;"> The fluxonium qubits have emerged as a promising platform for gate-based quantum information processing. However, their extraordinary protection against charge fluctuations comes at a cost: when coupled capacitively, the qubit-qubit interactions are restricted to XX-interactions. Consequently, effective XX- or XZ-interactions are only constructed either by temporarily populating higher-energy stat… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.16040v1-abstract-full').style.display = 'inline'; document.getElementById('2308.16040v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.16040v1-abstract-full" style="display: none;"> The fluxonium qubits have emerged as a promising platform for gate-based quantum information processing. However, their extraordinary protection against charge fluctuations comes at a cost: when coupled capacitively, the qubit-qubit interactions are restricted to XX-interactions. Consequently, effective XX- or XZ-interactions are only constructed either by temporarily populating higher-energy states, or by exploiting perturbative effects under microwave driving. Instead, we propose and demonstrate an inductive coupling scheme, which offers a wide selection of native qubit-qubit interactions for fluxonium. In particular, we leverage a built-in, flux-controlled ZZ-interaction to perform qubit entanglement. To combat the increased flux-noise-induced dephasing away from the flux-insensitive position, we use a continuous version of the dynamical decoupling scheme to perform noise filtering. Combining these, we demonstrate a 20 ns controlled-Z (CZ) gate with a mean fidelity of 99.53%. More than confirming the efficacy of our gate scheme, this high-fidelity result also reveals a promising but rarely explored parameter space uniquely suitable for gate operations between fluxonium qubits. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.16040v1-abstract-full').style.display = 'none'; document.getElementById('2308.16040v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.02252">arXiv:2308.02252</a> <span> [<a href="https://arxiv.org/pdf/2308.02252">pdf</a>, <a href="https://arxiv.org/format/2308.02252">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Measurement incompatibility cannot be stochastically distilled </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Hsieh%2C+C">Chung-Yun Hsieh</a>, <a href="/search/quant-ph?searchtype=author&query=Budroni%2C+C">Costantino Budroni</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.02252v2-abstract-short" style="display: inline;"> We show that the incompatibility of a set of measurements cannot be increased by subjecting them to a filter, namely, by combining them with a device that post-selects the incoming states on a fixed outcome of a stochastic transformation. This result holds for several measures of incompatibility, such as those based on robustness and convex weight. Expanding these ideas to Einstein-Podolsky-Rosen… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.02252v2-abstract-full').style.display = 'inline'; document.getElementById('2308.02252v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.02252v2-abstract-full" style="display: none;"> We show that the incompatibility of a set of measurements cannot be increased by subjecting them to a filter, namely, by combining them with a device that post-selects the incoming states on a fixed outcome of a stochastic transformation. This result holds for several measures of incompatibility, such as those based on robustness and convex weight. Expanding these ideas to Einstein-Podolsky-Rosen steering experiments, we are able to solve the problem of the maximum steerability obtained with respect to the most general local filters in a way that allows for an explicit calculation of the filter operation. Moreover, our results generalize to nonphysical maps, i.e., positive but not completely positive linear maps. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.02252v2-abstract-full').style.display = 'none'; document.getElementById('2308.02252v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">17 pages, 1 figure, comments welcome</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.05201">arXiv:2306.05201</a> <span> [<a href="https://arxiv.org/pdf/2306.05201">pdf</a>, <a href="https://arxiv.org/format/2306.05201">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s42005-024-01563-3">10.1038/s42005-024-01563-3 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Deep learning the hierarchy of steering measurement settings of qubit-pair states </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Wang%2C+H">Hong-Ming Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+J">Jie-Yien Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+H">Hong-Bin Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.05201v2-abstract-short" style="display: inline;"> Quantum steering has attracted increasing research attention because of its fundamental importance, as well as its applications in quantum information science. Here we leverage the power of the deep learning model to infer the steerability of quantum states with specific numbers of measurement settings, which form a hierarchical structure. A computational protocol consisting of iterative tests is… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.05201v2-abstract-full').style.display = 'inline'; document.getElementById('2306.05201v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.05201v2-abstract-full" style="display: none;"> Quantum steering has attracted increasing research attention because of its fundamental importance, as well as its applications in quantum information science. Here we leverage the power of the deep learning model to infer the steerability of quantum states with specific numbers of measurement settings, which form a hierarchical structure. A computational protocol consisting of iterative tests is constructed to overcome the optimization, meanwhile, generating the necessary training data. According to the responses of the well-trained models to the different physics-driven features encoding the states to be recognized, we can numerically conclude that the most compact characterization of the Alice-to-Bob steerability is Alice's regularly aligned steering ellipsoid; whereas Bob's ellipsoid is irrelevant. We have also provided an explanation to this result with the one-way stochastic local operations and classical communication. Additionally, our approach is versatile in revealing further insights into the hierarchical structure of quantum steering and detecting the hidden steerability. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.05201v2-abstract-full').style.display = 'none'; document.getElementById('2306.05201v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 8 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Commun. Phys. 7, 72 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.08110">arXiv:2302.08110</a> <span> [<a href="https://arxiv.org/pdf/2302.08110">pdf</a>, <a href="https://arxiv.org/format/2302.08110">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Characterization of loss mechanisms in a fluxonium qubit </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Sun%2C+H">Hantao Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+F">Feng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Ma%2C+X">Xizheng Ma</a>, <a href="/search/quant-ph?searchtype=author&query=Qin%2C+J">Jin Qin</a>, <a href="/search/quant-ph?searchtype=author&query=Song%2C+Z">Zhijun Song</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+T">Tenghui Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+G">Gengyan Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+J">Jingwei Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+Y">Yaoyun Shi</a>, <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+H">Hui-Hai Zhao</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+C">Chunqing Deng</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2302.08110v1-abstract-short" style="display: inline;"> Using a fluxonium qubit with in situ tunability of its Josephson energy, we characterize its energy relaxation at different flux biases as well as different Josephson energy values. The relaxation rate at qubit energy values, ranging more than one order of magnitude around the thermal energy $k_B T$, can be quantitatively explained by a combination of dielectric loss and $1/f$ flux noise with a cr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.08110v1-abstract-full').style.display = 'inline'; document.getElementById('2302.08110v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.08110v1-abstract-full" style="display: none;"> Using a fluxonium qubit with in situ tunability of its Josephson energy, we characterize its energy relaxation at different flux biases as well as different Josephson energy values. The relaxation rate at qubit energy values, ranging more than one order of magnitude around the thermal energy $k_B T$, can be quantitatively explained by a combination of dielectric loss and $1/f$ flux noise with a crossover point. The amplitude of the $1/f$ flux noise is consistent with that extracted from the qubit dephasing measurements at the flux sensitive points. In the dielectric loss dominant regime, the loss is consistent with that arises from the electric dipole interaction with two-level-system (TLS) defects. In particular, as increasing Josephson energy thus decreasing qubit frequency at the flux insensitive spot, we find that the qubit exhibits increasingly weaker coupling to TLS defects thus desirable for high-fidelity quantum operations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.08110v1-abstract-full').style.display = 'none'; document.getElementById('2302.08110v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.13438">arXiv:2211.13438</a> <span> [<a href="https://arxiv.org/pdf/2211.13438">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> </div> <p class="title is-5 mathjax"> Controllable tunability of a Chern number within the electronic-nuclear spin system in diamond </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Lee%2C+J">Junghyun Lee</a>, <a href="/search/quant-ph?searchtype=author&query=Arai%2C+K">Keigo Arai</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+H">Huiliang Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+M+J+H">Mark J. H. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Walsworth%2C+R+L">Ronald L. Walsworth</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2211.13438v1-abstract-short" style="display: inline;"> Chern numbers are gaining traction as they characterize topological phases in various physical systems. However, the resilience of the system topology to external perturbations makes it challenging to experimentally investigate transitions between different phases. In this study, we demonstrate the transitions of Chern number from 0 to 3, synthesized in an electronic-nuclear spin system associated… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.13438v1-abstract-full').style.display = 'inline'; document.getElementById('2211.13438v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.13438v1-abstract-full" style="display: none;"> Chern numbers are gaining traction as they characterize topological phases in various physical systems. However, the resilience of the system topology to external perturbations makes it challenging to experimentally investigate transitions between different phases. In this study, we demonstrate the transitions of Chern number from 0 to 3, synthesized in an electronic-nuclear spin system associated with the nitrogen-vacancy (NV) centre in diamond. The Chern number is characterized by the number of degeneracies enclosed in a control Hamiltonian parameter sphere. The topological transitions between different phases are depicted by varying the radius and offset of the sphere. We show that the measured topological phase diagram is not only consistent with the numerical calculations but can also be mapped onto an interacting three-qubit system. The NV system may also allow access to even higher Chern numbers, which can be applied to exploring exotic topology or topological quantum information. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.13438v1-abstract-full').style.display = 'none'; document.getElementById('2211.13438v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2206.05921">arXiv:2206.05921</a> <span> [<a href="https://arxiv.org/pdf/2206.05921">pdf</a>, <a href="https://arxiv.org/format/2206.05921">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.106.052201">10.1103/PhysRevA.106.052201 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Maxwell's two-demon engine under pure dephasing noise </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Chan%2C+F">Feng-Jui Chan</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+Y">Yi-Te Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+J">Jhen-Dong Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+J">Jui-Sheng Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+H">Hong-Bin Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2206.05921v2-abstract-short" style="display: inline;"> The interplay between thermal machines and quantum correlations is of great interest in both quantum thermodynamics and quantum information science. Recently, a quantum Szil谩rd engine has been proposed, showing that the quantum steerability between a Maxwell's demon and a work medium can be beneficial to a work extraction task. Nevertheless, this type of quantum-fueled machine is usually fragile i… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.05921v2-abstract-full').style.display = 'inline'; document.getElementById('2206.05921v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2206.05921v2-abstract-full" style="display: none;"> The interplay between thermal machines and quantum correlations is of great interest in both quantum thermodynamics and quantum information science. Recently, a quantum Szil谩rd engine has been proposed, showing that the quantum steerability between a Maxwell's demon and a work medium can be beneficial to a work extraction task. Nevertheless, this type of quantum-fueled machine is usually fragile in the presence of decoherence effects. We provide an example of the pure dephasing process, showing that the engine's quantumness can be degraded. Therefore, in this work, we tackle this question by introducing a second demon who can access a control system and make the work medium pass through two dephasing channels in a manner of quantum superposition. Furthermore, we provide a quantum circuit to simulate our proposed concept and test it on IBMQ and IonQ quantum computers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.05921v2-abstract-full').style.display = 'none'; document.getElementById('2206.05921v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 June, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 7 figures, 2 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 106, 052201 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2206.03760">arXiv:2206.03760</a> <span> [<a href="https://arxiv.org/pdf/2206.03760">pdf</a>, <a href="https://arxiv.org/ps/2206.03760">ps</a>, <a href="https://arxiv.org/format/2206.03760">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.5.013103">10.1103/PhysRevResearch.5.013103 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Steering-enhanced quantum metrology using superpositions of noisy phase shifts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Lee%2C+K">Kuan-Yi Lee</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+J">Jhen-Dong Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Miranowicz%2C+A">Adam Miranowicz</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2206.03760v4-abstract-short" style="display: inline;"> Quantum steering is an important correlation in quantum information theory. A recent work [Nat. Commun. 12, 2410 (2021)] showed that quantum steering is also useful for quantum metrology. Here, we extend the exploration of steering-enhanced quantum metrology from single noiseless phase shifts to superpositions of noisy phase shifts. As concrete examples, we consider a control system that manipulat… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.03760v4-abstract-full').style.display = 'inline'; document.getElementById('2206.03760v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2206.03760v4-abstract-full" style="display: none;"> Quantum steering is an important correlation in quantum information theory. A recent work [Nat. Commun. 12, 2410 (2021)] showed that quantum steering is also useful for quantum metrology. Here, we extend the exploration of steering-enhanced quantum metrology from single noiseless phase shifts to superpositions of noisy phase shifts. As concrete examples, we consider a control system that manipulates a target system to pass through a superposition of either dephased or depolarized phase shifts channels. We show that using such superpositions of noisy phase shifts can suppress the effects of noise and improve metrology. Furthermore, we also implemented proof-of-principle experiments for a superposition of dephased phase shifts on the IBM Quantum Experience, demonstrating a clear improvement on metrology. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.03760v4-abstract-full').style.display = 'none'; document.getElementById('2206.03760v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 8 June, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 5, 013103 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.03528">arXiv:2205.03528</a> <span> [<a href="https://arxiv.org/pdf/2205.03528">pdf</a>, <a href="https://arxiv.org/format/2205.03528">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Superconductivity">cond-mat.supr-con</span> </div> </div> <p class="title is-5 mathjax"> Titanium Nitride Film on Sapphire Substrate with Low Dielectric Loss for Superconducting Qubits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Deng%2C+H">Hao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Song%2C+Z">Zhijun Song</a>, <a href="/search/quant-ph?searchtype=author&query=Gao%2C+R">Ran Gao</a>, <a href="/search/quant-ph?searchtype=author&query=Xia%2C+T">Tian Xia</a>, <a href="/search/quant-ph?searchtype=author&query=Bao%2C+F">Feng Bao</a>, <a href="/search/quant-ph?searchtype=author&query=Jiang%2C+X">Xun Jiang</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+Z">Zhisheng Li</a>, <a href="/search/quant-ph?searchtype=author&query=Ma%2C+X">Xizheng Ma</a>, <a href="/search/quant-ph?searchtype=author&query=Qin%2C+J">Jin Qin</a>, <a href="/search/quant-ph?searchtype=author&query=Sun%2C+H">Hantao Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Tang%2C+C">Chengchun Tang</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+T">Tenghui Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+F">Feng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+W">Wenlong Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+G">Gengyan Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+X">Xiaohang Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+J">Jingwei Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Zhu%2C+X">Xing Zhu</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+Y">Yaoyun Shi</a>, <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+H">Hui-Hai Zhao</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+C">Chunqing Deng</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.03528v1-abstract-short" style="display: inline;"> Dielectric loss is one of the major decoherence sources of superconducting qubits. Contemporary high-coherence superconducting qubits are formed by material systems mostly consisting of superconducting films on substrate with low dielectric loss, where the loss mainly originates from the surfaces and interfaces. Among the multiple candidates for material systems, a combination of titanium nitride… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.03528v1-abstract-full').style.display = 'inline'; document.getElementById('2205.03528v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.03528v1-abstract-full" style="display: none;"> Dielectric loss is one of the major decoherence sources of superconducting qubits. Contemporary high-coherence superconducting qubits are formed by material systems mostly consisting of superconducting films on substrate with low dielectric loss, where the loss mainly originates from the surfaces and interfaces. Among the multiple candidates for material systems, a combination of titanium nitride (TiN) film and sapphire substrate has good potential because of its chemical stability against oxidization, and high quality at interfaces. In this work, we report a TiN film deposited onto sapphire substrate achieving low dielectric loss at the material interface. Through the systematic characterizations of a series of transmon qubits fabricated with identical batches of TiN base layers, but different geometries of qubit shunting capacitors with various participation ratios of the material interface, we quantitatively extract the loss tangent value at the substrate-metal interface smaller than $8.9 \times 10^{-4}$ in 1-nm disordered layer. By optimizing the interface participation ratio of the transmon qubit, we reproducibly achieve qubit lifetimes of up to 300 $渭$s and quality factors approaching 8 million. We demonstrate that TiN film on sapphire substrate is an ideal material system for high-coherence superconducting qubits. Our analyses further suggest that the interface dielectric loss around the Josephson junction part of the circuit could be the dominant limitation of lifetimes for state-of-the-art transmon qubits. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.03528v1-abstract-full').style.display = 'none'; document.getElementById('2205.03528v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2203.07610">arXiv:2203.07610</a> <span> [<a href="https://arxiv.org/pdf/2203.07610">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Dressed-state control of effective dipolar interaction between strongly-coupled solid-state spins </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Lee%2C+J">Junghyun Lee</a>, <a href="/search/quant-ph?searchtype=author&query=Tatsuta%2C+M">Mamiko Tatsuta</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+A">Andrew Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Bauch%2C+E">Erik Bauch</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+M+J+H">Mark J. H. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Walsworth%2C+R+L">Ronald. L. Walsworth</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2203.07610v2-abstract-short" style="display: inline;"> Strong interactions between spins in many-body solid-state quantum system is a crucial resource for exploring and applying non-classical states. In particular, electronic spins associated with defects in diamond system are a leading platform for the study of collective quantum phenomena and for quantum technology applications. While such solid-state quantum defect systems have the advantage of sca… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.07610v2-abstract-full').style.display = 'inline'; document.getElementById('2203.07610v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.07610v2-abstract-full" style="display: none;"> Strong interactions between spins in many-body solid-state quantum system is a crucial resource for exploring and applying non-classical states. In particular, electronic spins associated with defects in diamond system are a leading platform for the study of collective quantum phenomena and for quantum technology applications. While such solid-state quantum defect systems have the advantage of scalability and operation under ambient conditions, they face the key challenge of controlling interactions between the defects spins, since the defects are spatially fixed inside the host lattice with relative positions that cannot be well controlled during fabrication. In this work, we present a dressed-state approach to control the effective dipolar coupling between solid-state spins; and then demonstrate this scheme experimentally using two strongly-coupled nitrogen vacancy (NV) centers in diamond. Including Rabi driving terms between the m$_s$ = 0 and $\pm$1 states in the NV spin Hamiltonian allows us to turn on and off or tune the effective dipolar coupling between two NV spins. Through Ramsey spectroscopy, we detect the change of the effective dipolar field generated by the control NV spin prepared in different dressed states. To observe the change of interaction dynamics, we then deploy spin-lock-based polarization transfer measurements via a Hartmann-Hahn matching condition between two NV spins in different dressed states. We perform simulations that indicate the promise for this robust scheme to control the distribution of interaction strengths in strongly-interacting spin systems, including interaction strength homogenization in a spin ensemble, which can be a valuable tool for studying non-equilibrium quantum phases and generating high fidelity multi-spin correlated states for quantum-enhanced sensing. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.07610v2-abstract-full').style.display = 'none'; document.getElementById('2203.07610v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 14 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.07691">arXiv:2201.07691</a> <span> [<a href="https://arxiv.org/pdf/2201.07691">pdf</a>, <a href="https://arxiv.org/ps/2201.07691">ps</a>, <a href="https://arxiv.org/format/2201.07691">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41467-022-32466-y">10.1038/s41467-022-32466-y <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Complete classification of steerability under local filters and its relation with measurement incompatibility </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Hsieh%2C+C">Chung-Yun Hsieh</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Budroni%2C+C">Costantino Budroni</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2201.07691v2-abstract-short" style="display: inline;"> Quantum steering is the central resource for one-sided device-independent quantum information. It is manipulated via one-way local operations and classical communication, such as local filtering on the trusted party. Here, we provide a necessary and sufficient condition for a steering assemblage to be transformable into another one via local filtering. We characterize the equivalence classes with… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.07691v2-abstract-full').style.display = 'inline'; document.getElementById('2201.07691v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.07691v2-abstract-full" style="display: none;"> Quantum steering is the central resource for one-sided device-independent quantum information. It is manipulated via one-way local operations and classical communication, such as local filtering on the trusted party. Here, we provide a necessary and sufficient condition for a steering assemblage to be transformable into another one via local filtering. We characterize the equivalence classes with respect to filters in terms of the steering equivalent observables measurement assemblage (SEO), first proposed to connect the problem of steerability with measurement incompatibility. We provide an efficient method to compute the maximal extractable steerability via local filters and show that it coincides with the incompatibility of the SEO. Moreover, we show that there always exists a bipartite state that provides an assemblage with steerability equal to the incompatibility of the measurements on the untrusted party. Finally, we investigate the optimal success probability and rates for transformation protocols (distillation and dilution) in the single-shot scenario together with examples. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.07691v2-abstract-full').style.display = 'none'; document.getElementById('2201.07691v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages, 2 figures, comments welcome!</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature communications 13, 4973 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.13504">arXiv:2111.13504</a> <span> [<a href="https://arxiv.org/pdf/2111.13504">pdf</a>, <a href="https://arxiv.org/format/2111.13504">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.129.010502">10.1103/PhysRevLett.129.010502 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Fluxonium: an alternative qubit platform for high-fidelity operations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Bao%2C+F">Feng Bao</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+H">Hao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Ding%2C+D">Dawei Ding</a>, <a href="/search/quant-ph?searchtype=author&query=Gao%2C+R">Ran Gao</a>, <a href="/search/quant-ph?searchtype=author&query=Gao%2C+X">Xun Gao</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+C">Cupjin Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Jiang%2C+X">Xun Jiang</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+Z">Zhisheng Li</a>, <a href="/search/quant-ph?searchtype=author&query=Ma%2C+X">Xizheng Ma</a>, <a href="/search/quant-ph?searchtype=author&query=Ni%2C+X">Xiaotong Ni</a>, <a href="/search/quant-ph?searchtype=author&query=Qin%2C+J">Jin Qin</a>, <a href="/search/quant-ph?searchtype=author&query=Song%2C+Z">Zhijun Song</a>, <a href="/search/quant-ph?searchtype=author&query=Sun%2C+H">Hantao Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Tang%2C+C">Chengchun Tang</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+T">Tenghui Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+F">Feng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Xia%2C+T">Tian Xia</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+W">Wenlong Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+F">Fang Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+G">Gengyan Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+X">Xiaohang Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+J">Jingwei Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Zhu%2C+X">Xing Zhu</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+Y">Yaoyun Shi</a> , et al. (3 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2111.13504v2-abstract-short" style="display: inline;"> Superconducting qubits provide a promising path toward building large-scale quantum computers. The simple and robust transmon qubit has been the leading platform, achieving multiple milestones. However, fault-tolerant quantum computing calls for qubit operations at error rates significantly lower than those exhibited in the state of the art. Consequently, alternative superconducting qubits with be… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.13504v2-abstract-full').style.display = 'inline'; document.getElementById('2111.13504v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.13504v2-abstract-full" style="display: none;"> Superconducting qubits provide a promising path toward building large-scale quantum computers. The simple and robust transmon qubit has been the leading platform, achieving multiple milestones. However, fault-tolerant quantum computing calls for qubit operations at error rates significantly lower than those exhibited in the state of the art. Consequently, alternative superconducting qubits with better error protection have attracted increasing interest. Among them, fluxonium is a particularly promising candidate, featuring large anharmonicity and long coherence times. Here, we engineer a fluxonium-based quantum processor that integrates high qubit-coherence, fast frequency-tunability, and individual-qubit addressability for reset, readout, and gates. With simple and fast gate schemes, we achieve an average single-qubit gate fidelity of 99.97% and a two-qubit gate fidelity of up to 99.72%. This performance is comparable to the highest values reported in the literature of superconducting circuits. Thus our work, for the first time within the realm of superconducting qubits, reveals an approach toward fault-tolerant quantum computing that is alternative and competitive to the transmon system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.13504v2-abstract-full').style.display = 'none'; document.getElementById('2111.13504v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Lett. 129, 010502 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.05088">arXiv:2111.05088</a> <span> [<a href="https://arxiv.org/pdf/2111.05088">pdf</a>, <a href="https://arxiv.org/format/2111.05088">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Superconductivity">cond-mat.supr-con</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1002/adma.202201268">10.1002/adma.202201268 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ultrahigh-inductance materials from spinodal decomposition </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Gao%2C+R">Ran Gao</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+H">Hao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+W">Wenlong Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Xia%2C+T">Tian Xia</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+F">Feng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Song%2C+Z">Zhijun Song</a>, <a href="/search/quant-ph?searchtype=author&query=Miao%2C+X">Xiaohe Miao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+C">Chao Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+Y">Yue Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+Y">Yaoyun Shi</a>, <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+H">Hui-Hai Zhao</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+C">Chunqing Deng</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2111.05088v2-abstract-short" style="display: inline;"> Disordered superconducting nitrides with kinetic inductance have long been considered a leading material candidate for high-inductance quantum-circuit applications. Despite continuing efforts in reducing material dimensions to increase the kinetic inductance and the corresponding circuit impedance, it becomes a fundamental challenge to improve further without compromising material qualities. To th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.05088v2-abstract-full').style.display = 'inline'; document.getElementById('2111.05088v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.05088v2-abstract-full" style="display: none;"> Disordered superconducting nitrides with kinetic inductance have long been considered a leading material candidate for high-inductance quantum-circuit applications. Despite continuing efforts in reducing material dimensions to increase the kinetic inductance and the corresponding circuit impedance, it becomes a fundamental challenge to improve further without compromising material qualities. To this end, we propose a method to drastically increase the kinetic inductance of superconducting materials via spinodal decomposition while keeping a low microwave loss. We use epitaxial Ti\textsubscript{0.48}Al\textsubscript{0.52}N as a model system, and for the first time demonstrate the utilization of spinodal decomposition to trigger the insulator-to-superconductor transition with a drastically enhanced material disorder. The measured kinetic inductance has increased by 2-3 orders of magnitude compared with all the best reported disordered superconducting nitrides. Our work paves the way for substantially enhancing and deterministically controlling the inductance for advanced superconducting quantum circuits. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.05088v2-abstract-full').style.display = 'none'; document.getElementById('2111.05088v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.04227">arXiv:2111.04227</a> <span> [<a href="https://arxiv.org/pdf/2111.04227">pdf</a>, <a href="https://arxiv.org/format/2111.04227">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevMaterials.6.036202">10.1103/PhysRevMaterials.6.036202 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Epitaxial titanium nitride microwave resonators: Structural, chemical, electrical, and microwave properties </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Gao%2C+R">Ran Gao</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+W">Wenlong Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+H">Hao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+Z">Zhisheng Li</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+M">Minghua Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Miao%2C+X">Xiaohe Miao</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+Y">Yue Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+C">Chunqing Deng</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2111.04227v4-abstract-short" style="display: inline;"> Titanium nitride is an attractive material for a range of superconducting quantum-circuit applications owing to its low microwave losses, high surface inductance, and chemical stability. The physical properties and device performance, nevertheless, depend strongly on the quality of the materials. Here we focus on the highly crystalline and epitaxial titanium nitride thin films deposited on sapphir… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.04227v4-abstract-full').style.display = 'inline'; document.getElementById('2111.04227v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.04227v4-abstract-full" style="display: none;"> Titanium nitride is an attractive material for a range of superconducting quantum-circuit applications owing to its low microwave losses, high surface inductance, and chemical stability. The physical properties and device performance, nevertheless, depend strongly on the quality of the materials. Here we focus on the highly crystalline and epitaxial titanium nitride thin films deposited on sapphire substrates using magnetron sputtering at an intermediate temperature (300$^{\circ}$C). We perform a set of systematic and comprehensive material characterization to thoroughly understand the structural, chemical, and transport properties. Microwave losses at low temperatures are studied using patterned microwave resonators, where the best internal quality factor in the single-photon regime is measured to be $3.3\times 10^6$, and $> 1.0\times 10^7$ in the high-power regime. Adjusted with the material filling factor of the resonators, the microwave loss-tangent here compares well with the previously reported best values for superconducting resonators. This work lays the foundation of using epitaxial titanium nitride for low-loss superconducting quantum circuits. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.04227v4-abstract-full').style.display = 'none'; document.getElementById('2111.04227v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review MATERIALS 6, 036202 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.03865">arXiv:2108.03865</a> <span> [<a href="https://arxiv.org/pdf/2108.03865">pdf</a>, <a href="https://arxiv.org/ps/2108.03865">ps</a>, <a href="https://arxiv.org/format/2108.03865">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.105.042610">10.1103/PhysRevA.105.042610 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Deterministic one-way logic gates on a cloud quantum computer </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Yang%2C+Z">Zhi-Peng Yang</a>, <a href="/search/quant-ph?searchtype=author&query=Baishya%2C+A">Alakesh Baishya</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+Y">Yu-Ran Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Kockum%2C+A+F">Anton Frisk Kockum</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+F">Fu-Li Li</a>, <a href="/search/quant-ph?searchtype=author&query=Tsai%2C+J">Jaw-Shen Tsai</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2108.03865v2-abstract-short" style="display: inline;"> One-way quantum computing is a promising candidate for fault-tolerant quantum computing. Here, we propose new protocols to realize a deterministic one-way CNOT gate and one-way $X$-rotations on quantum-computing platforms. By applying a delayed-choice scheme, we overcome a limit of most currently available quantum computers, which are unable to implement further operations on measured qubits or op… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.03865v2-abstract-full').style.display = 'inline'; document.getElementById('2108.03865v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.03865v2-abstract-full" style="display: none;"> One-way quantum computing is a promising candidate for fault-tolerant quantum computing. Here, we propose new protocols to realize a deterministic one-way CNOT gate and one-way $X$-rotations on quantum-computing platforms. By applying a delayed-choice scheme, we overcome a limit of most currently available quantum computers, which are unable to implement further operations on measured qubits or operations conditioned on measurement results from other qubits. Moreover, we decrease the error rate of the one-way logic gates, compared to the original protocol using local operations and classical communication (LOCC). In addition, we apply our deterministic one-way CNOT gate in the Deutsch-Jozsa algorithm to show the feasibility of our proposal. We demonstrate all these one-way gates and algorithms by running experiments on the cloud quantum-computing platform IBM Quantum Experience. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.03865v2-abstract-full').style.display = 'none'; document.getElementById('2108.03865v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review A 105, 042610 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.00304">arXiv:2108.00304</a> <span> [<a href="https://arxiv.org/pdf/2108.00304">pdf</a>, <a href="https://arxiv.org/ps/2108.00304">ps</a>, <a href="https://arxiv.org/format/2108.00304">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Experiment">hep-ex</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Detectors">physics.ins-det</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevApplied.17.024041">10.1103/PhysRevApplied.17.024041 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> High-precision mapping of diamond crystal strain using quantum interferometry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Marshall%2C+M+C">Mason C. Marshall</a>, <a href="/search/quant-ph?searchtype=author&query=Ebadi%2C+R">Reza Ebadi</a>, <a href="/search/quant-ph?searchtype=author&query=Hart%2C+C">Connor Hart</a>, <a href="/search/quant-ph?searchtype=author&query=Turner%2C+M+J">Matthew J. Turner</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+M+J+H">Mark J. H. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Phillips%2C+D+F">David F. Phillips</a>, <a href="/search/quant-ph?searchtype=author&query=Walsworth%2C+R+L">Ronald L. Walsworth</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2108.00304v2-abstract-short" style="display: inline;"> Crystal strain variation imposes significant limitations on many quantum sensing and information applications for solid-state defect qubits in diamond. Thus, precision measurement and control of diamond crystal strain is a key challenge. Here, we report diamond strain measurements with a unique set of capabilities, including micron-scale spatial resolution, millimeter-scale field-of-view, and a tw… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.00304v2-abstract-full').style.display = 'inline'; document.getElementById('2108.00304v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.00304v2-abstract-full" style="display: none;"> Crystal strain variation imposes significant limitations on many quantum sensing and information applications for solid-state defect qubits in diamond. Thus, precision measurement and control of diamond crystal strain is a key challenge. Here, we report diamond strain measurements with a unique set of capabilities, including micron-scale spatial resolution, millimeter-scale field-of-view, and a two order-of-magnitude improvement in volume-normalized sensitivity over previous work [1], reaching $5(2) \times 10^{-8}/\sqrt{\rm{Hz}\cdot\rm{渭m}^3}$ (with spin-strain coupling coefficients representing the dominant systematic uncertainty). We use strain-sensitive spin-state interferometry on ensembles of nitrogen vacancy (NV) color centers in single-crystal CVD bulk diamond with low strain gradients. This quantum interferometry technique provides insensitivity to magnetic-field inhomogeneity from the electronic and nuclear spin bath, thereby enabling long NV ensemble electronic spin dephasing times and enhanced strain sensitivity. We demonstrate the strain-sensitive measurement protocol first on a scanning confocal laser microscope, providing quantitative measurement of sensitivity as well as three-dimensional strain mapping; and second on a wide-field imaging quantum diamond microscope (QDM). Our strain microscopy technique enables fast, sensitive characterization for diamond material engineering and nanofabrication; as well as diamond-based sensing of strains applied externally, as in diamond anvil cells or embedded diamond stress sensors, or internally, as by crystal damage due to particle-induced nuclear recoils. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.00304v2-abstract-full').style.display = 'none'; document.getElementById('2108.00304v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 31 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Applied 17, 024041 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.15784">arXiv:2106.15784</a> <span> [<a href="https://arxiv.org/pdf/2106.15784">pdf</a>, <a href="https://arxiv.org/format/2106.15784">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PRXQuantum.3.020338">10.1103/PRXQuantum.3.020338 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantifying Quantumness of Channels Without Entanglement </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Kadlec%2C+J">Josef Kadlec</a>, <a href="/search/quant-ph?searchtype=author&query=%C4%8Cernoch%2C+A">Anton铆n 膶ernoch</a>, <a href="/search/quant-ph?searchtype=author&query=Quintino%2C+M+T">Marco T煤lio Quintino</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+W">Wenbin Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Lemr%2C+K">Karel Lemr</a>, <a href="/search/quant-ph?searchtype=author&query=Lambert%2C+N">Neill Lambert</a>, <a href="/search/quant-ph?searchtype=author&query=Miranowicz%2C+A">Adam Miranowicz</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2106.15784v5-abstract-short" style="display: inline;"> Quantum channels breaking entanglement, incompatibility, or nonlocality are defined as such because they are not useful for entanglement-based, one-sided device-independent, or device-independent quantum information processing, respectively. Here, we show that such breaking channels are related to complementary tests of macrorealism i.e., temporal separability, channel unsteerability, temporal uns… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.15784v5-abstract-full').style.display = 'inline'; document.getElementById('2106.15784v5-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.15784v5-abstract-full" style="display: none;"> Quantum channels breaking entanglement, incompatibility, or nonlocality are defined as such because they are not useful for entanglement-based, one-sided device-independent, or device-independent quantum information processing, respectively. Here, we show that such breaking channels are related to complementary tests of macrorealism i.e., temporal separability, channel unsteerability, temporal unsteerability, and the temporal Bell inequality. To demonstrate this we first define a steerability-breaking channel, which is conceptually similar to entanglement and nonlocality-breaking channels and prove that it is identical to an incompatibility-breaking channel. A hierarchy of quantum non-breaking channels is derived, akin to the existing hierarchy relations for temporal and spatial quantum correlations. We then introduce the concept of channels that break temporal correlations, explain how they are related to the standard breaking channels, and prove the following results: (1) A robustness-based measure for non-entanglement-breaking channels can be probed by temporal nonseparability. (2) A non-steerability-breaking channel can be quantified by channel steering. (3) Temporal steerability and non-macrorealism can be used for, respectively, distinguishing unital steerability-breaking channels and nonlocality-breaking channels for a maximally entangled state. Finally, a two-dimensional depolarizing channel is experimentally implemented as a proof-of-principle example to demonstrate the hierarchy relation of non-breaking channels using temporal quantum correlations <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.15784v5-abstract-full').style.display = 'none'; document.getElementById('2106.15784v5-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 December, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Comments welcome</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> PRX Quantum 3, 020338 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2105.08273">arXiv:2105.08273</a> <span> [<a href="https://arxiv.org/pdf/2105.08273">pdf</a>, <a href="https://arxiv.org/ps/2105.08273">ps</a>, <a href="https://arxiv.org/format/2105.08273">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.3.043083">10.1103/PhysRevResearch.3.043083 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Hidden nonmacrorealism: reviving the Leggett-Garg inequality with stochastic operations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Weng%2C+H">Hao-Cheng Weng</a>, <a href="/search/quant-ph?searchtype=author&query=Shih%2C+Y">Yen-An Shih</a>, <a href="/search/quant-ph?searchtype=author&query=Kuo%2C+P">Po-Chen Kuo</a>, <a href="/search/quant-ph?searchtype=author&query=Lambert%2C+N">Neill Lambert</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a>, <a href="/search/quant-ph?searchtype=author&query=Chuu%2C+C">Chih-Sung Chuu</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2105.08273v3-abstract-short" style="display: inline;"> The Leggett-Garg inequality (LGI) distinguishes nonmacrorealistic channels from macrorealistic ones by constraining the experimental outcomes of the underlying system. In this work, we propose a class of channels which, initially, cannot violate the LGI (in the form of the temporal Bell inequality) but can violate it after the application of stochastic pre- and post- operations (SPPOs). As a proof… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.08273v3-abstract-full').style.display = 'inline'; document.getElementById('2105.08273v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2105.08273v3-abstract-full" style="display: none;"> The Leggett-Garg inequality (LGI) distinguishes nonmacrorealistic channels from macrorealistic ones by constraining the experimental outcomes of the underlying system. In this work, we propose a class of channels which, initially, cannot violate the LGI (in the form of the temporal Bell inequality) but can violate it after the application of stochastic pre- and post- operations (SPPOs). As a proof-of-principle experiment, we demonstrate the stochastic pre- and post- operations in an amplitude-damping channel with photonic qubits. We denote the above phenomenon as hidden nonmacrorealistic channels. We also discuss the relationship between this hidden nonmacrorealistic channels (in terms of the temporal Clauser-Horne-Shimony-Holt (CHSH) inequality) and the strongly nonlocality-breaking channel, which breaks the hidden spatial CHSH nonlocality for arbitrary states. In general, if the channel satisfies hidden nonmacrorealism, it is not a strongly CHSH nonlocality-breaking channel. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.08273v3-abstract-full').style.display = 'none'; document.getElementById('2105.08273v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 31 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Comments welcome</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 3, 043083 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.12305">arXiv:2103.12305</a> <span> [<a href="https://arxiv.org/pdf/2103.12305">pdf</a>, <a href="https://arxiv.org/format/2103.12305">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> A universal quantum gate set for transmon qubits with strong ZZ interactions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Long%2C+J">Junling Long</a>, <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+T">Tongyu Zhao</a>, <a href="/search/quant-ph?searchtype=author&query=Bal%2C+M">Mustafa Bal</a>, <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+R">Ruichen Zhao</a>, <a href="/search/quant-ph?searchtype=author&query=Barron%2C+G+S">George S. Barron</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Howard%2C+J+A">Joel A. Howard</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+X">Xian Wu</a>, <a href="/search/quant-ph?searchtype=author&query=McRae%2C+C+R+H">Corey Rae H. McRae</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+X">Xiu-Hao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Ribeill%2C+G+J">Guilhem J. Ribeill</a>, <a href="/search/quant-ph?searchtype=author&query=Singh%2C+M">Meenakshi Singh</a>, <a href="/search/quant-ph?searchtype=author&query=Ohki%2C+T+A">Thomas A. Ohki</a>, <a href="/search/quant-ph?searchtype=author&query=Barnes%2C+E">Edwin Barnes</a>, <a href="/search/quant-ph?searchtype=author&query=Economou%2C+S+E">Sophia E. Economou</a>, <a href="/search/quant-ph?searchtype=author&query=Pappas%2C+D+P">David P. Pappas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2103.12305v1-abstract-short" style="display: inline;"> High-fidelity single- and two-qubit gates are essential building blocks for a fault-tolerant quantum computer. While there has been much progress in suppressing single-qubit gate errors in superconducting qubit systems, two-qubit gates still suffer from error rates that are orders of magnitude higher. One limiting factor is the residual ZZ-interaction, which originates from a coupling between comp… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.12305v1-abstract-full').style.display = 'inline'; document.getElementById('2103.12305v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.12305v1-abstract-full" style="display: none;"> High-fidelity single- and two-qubit gates are essential building blocks for a fault-tolerant quantum computer. While there has been much progress in suppressing single-qubit gate errors in superconducting qubit systems, two-qubit gates still suffer from error rates that are orders of magnitude higher. One limiting factor is the residual ZZ-interaction, which originates from a coupling between computational states and higher-energy states. While this interaction is usually viewed as a nuisance, here we experimentally demonstrate that it can be exploited to produce a universal set of fast single- and two-qubit entangling gates in a coupled transmon qubit system. To implement arbitrary single-qubit rotations, we design a new protocol called the two-axis gate that is based on a three-part composite pulse. It rotates a single qubit independently of the state of the other qubit despite the strong ZZ-coupling. We achieve single-qubit gate fidelities as high as 99.1% from randomized benchmarking measurements. We then demonstrate both a CZ gate and a CNOT gate. Because the system has a strong ZZ-interaction, a CZ gate can be achieved by letting the system freely evolve for a gate time $t_g=53.8$ ns. To design the CNOT gate, we utilize an analytical microwave pulse shape based on the SWIPHT protocol for realizing fast, low-leakage gates. We obtain fidelities of 94.6% and 97.8% for the CNOT and CZ gates respectively from quantum progress tomography. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.12305v1-abstract-full').style.display = 'none'; document.getElementById('2103.12305v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.08388">arXiv:2103.08388</a> <span> [<a href="https://arxiv.org/pdf/2103.08388">pdf</a>, <a href="https://arxiv.org/ps/2103.08388">ps</a>, <a href="https://arxiv.org/format/2103.08388">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevApplied.16.054032">10.1103/PhysRevApplied.16.054032 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Scanning X-ray Diffraction Microscopy for Diamond Quantum Sensing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Marshall%2C+M+C">Mason C. Marshall</a>, <a href="/search/quant-ph?searchtype=author&query=Phillips%2C+D+F">David F. Phillips</a>, <a href="/search/quant-ph?searchtype=author&query=Turner%2C+M+J">Matthew J. Turner</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+M+J+H">Mark J. H. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+T">Tao Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Delegan%2C+N">Nazar Delegan</a>, <a href="/search/quant-ph?searchtype=author&query=Heremans%2C+F+J">F. Joseph Heremans</a>, <a href="/search/quant-ph?searchtype=author&query=Holt%2C+M+V">Martin V. Holt</a>, <a href="/search/quant-ph?searchtype=author&query=Walsworth%2C+R+L">Ronald L. Walsworth</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2103.08388v3-abstract-short" style="display: inline;"> Understanding nano- and micro-scale crystal strain in CVD diamond is crucial to the advancement of diamond quantum technologies. In particular, the presence of such strain and its characterization present a challenge to diamond-based quantum sensing and information applications -- as well as for future dark matter detectors where directional information of incoming particles is encoded in crystal… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.08388v3-abstract-full').style.display = 'inline'; document.getElementById('2103.08388v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.08388v3-abstract-full" style="display: none;"> Understanding nano- and micro-scale crystal strain in CVD diamond is crucial to the advancement of diamond quantum technologies. In particular, the presence of such strain and its characterization present a challenge to diamond-based quantum sensing and information applications -- as well as for future dark matter detectors where directional information of incoming particles is encoded in crystal strain. Here, we exploit nanofocused scanning X-ray diffraction microscopy to quantitatively measure crystal deformation from defects in diamond with high spatial and strain resolution. Combining information from multiple Bragg angles allows stereoscopic three-dimensional modeling of strain feature geometry; the diffraction results are validated via comparison to optical measurements of the strain tensor based on spin-state-dependent spectroscopy of ensembles of nitrogen vacancy (NV) centers in the diamond. Our results demonstrate both strain and spatial resolution sufficient for directional detection of dark matter via X-ray measurement of crystal strain, and provide a promising tool for diamond growth analysis and improvement of defect-based sensing. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.08388v3-abstract-full').style.display = 'none'; document.getElementById('2103.08388v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Applied 16, 054032 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2011.10564">arXiv:2011.10564</a> <span> [<a href="https://arxiv.org/pdf/2011.10564">pdf</a>, <a href="https://arxiv.org/format/2011.10564">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevB.103.174501">10.1103/PhysRevB.103.174501 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Free Mode Removal and Mode Decoupling for Simulating General Superconducting Quantum Circuits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ding%2C+D">Dawei Ding</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+Y">Yaoyun Shi</a>, <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+H">Hui-Hai Zhao</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2011.10564v3-abstract-short" style="display: inline;"> Superconducting quantum circuits is one of the leading candidates for a universal quantum computer. Designing novel qubit and multiqubit superconducting circuits requires the ability to simulate and analyze the properties of a general circuit. In particular, going outside the transmon approach, we cannot make assumptions on anharmonicity, thus precluding blackbox quantization approaches and necess… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.10564v3-abstract-full').style.display = 'inline'; document.getElementById('2011.10564v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2011.10564v3-abstract-full" style="display: none;"> Superconducting quantum circuits is one of the leading candidates for a universal quantum computer. Designing novel qubit and multiqubit superconducting circuits requires the ability to simulate and analyze the properties of a general circuit. In particular, going outside the transmon approach, we cannot make assumptions on anharmonicity, thus precluding blackbox quantization approaches and necessitating the formal circuit quantization approach. We consider and solve two issues involved in simulating general superconducting circuits. One of the issues is the handling of free modes in the circuit, that is, circuit modes with no potential term in the Hamiltonian. Another issue is circuit size, namely the challenge of simulating strongly coupled multimode circuits. The main mathematical tool we use to address these issues is the linear canonical transformation in the setting of quantum mechanics. We address the first issue by giving a provably correct algorithm for removing free modes by performing a linear canonical transformation to completely decouple the free modes from other circuit modes. We address the second by giving a series of different linear canonical transformations to reduce intermode couplings, thereby reducing the problem to the weakly coupled case and greatly mitigating the overhead for classical simulation. We benchmark our decoupling methods by applying them to the circuit of two inductively coupled fluxonium qubits, obtaining several orders of magnitude reduction in the size of the Hilbert space that needs to be simulated. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.10564v3-abstract-full').style.display = 'none'; document.getElementById('2011.10564v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 20 November, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. B 103, 174501 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2009.07425">arXiv:2009.07425</a> <span> [<a href="https://arxiv.org/pdf/2009.07425">pdf</a>, <a href="https://arxiv.org/format/2009.07425">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.3.023038">10.1103/PhysRevResearch.3.023038 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Benchmarking Quantum State Transfer on Quantum Devices using Spatio-Temporal Steering </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Huang%2C+Y">Yi-Te Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+J">Jhen-Dong Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2009.07425v4-abstract-short" style="display: inline;"> Quantum state transfer (QST) provides a method to send arbitrary quantum states from one system to another. Such a concept is crucial for transmitting quantum information into the quantum memory, quantum processor, and quantum network. The standard benchmark of QST is the average fidelity between the prepared and received states. In this work, we provide a new benchmark which reveals the non-class… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2009.07425v4-abstract-full').style.display = 'inline'; document.getElementById('2009.07425v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2009.07425v4-abstract-full" style="display: none;"> Quantum state transfer (QST) provides a method to send arbitrary quantum states from one system to another. Such a concept is crucial for transmitting quantum information into the quantum memory, quantum processor, and quantum network. The standard benchmark of QST is the average fidelity between the prepared and received states. In this work, we provide a new benchmark which reveals the non-classicality of QST based on spatio-temporal steering (STS). More specifically, we show that the local-hidden-state (LHS) model in STS can be viewed as the classical strategy of state transfer. Therefore, we can quantify the non-classicality of QST process by measuring the spatio-temporal steerability. We then apply the spatio-temporal steerability measurement technique to benchmark quantum devices including the IBM quantum experience and QuTech quantum inspire under QST tasks. The experimental results show that the spatio-temporal steerability decreases as the circuit depth increases, and the reduction agrees with the noise model, which refers to the accumulation of errors during the QST process. Moreover, we provide a quantity to estimate the signaling effect which could result from gate errors or intrinsic non-Markovian effect of the devices. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2009.07425v4-abstract-full').style.display = 'none'; document.getElementById('2009.07425v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages, 5 figures, 2 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 3, 023038 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2003.07043">arXiv:2003.07043</a> <span> [<a href="https://arxiv.org/pdf/2003.07043">pdf</a>, <a href="https://arxiv.org/ps/2003.07043">ps</a>, <a href="https://arxiv.org/format/2003.07043">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.104.022614">10.1103/PhysRevA.104.022614 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum steering as a witness of quantum scrambling </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Lin%2C+J">Jhen-Dong Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+W">Wei-Yu Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Lambert%2C+N">Neill Lambert</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2003.07043v3-abstract-short" style="display: inline;"> Quantum information scrambling describes the delocalization of local information to global information in the form of entanglement throughout all possible degrees of freedom. A natural measure of scrambling is the tripartite mutual information (TMI), which quantifies the amount of delocalized information for a given quantum channel with its state representation, i.e., the Choi state. In this work,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2003.07043v3-abstract-full').style.display = 'inline'; document.getElementById('2003.07043v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2003.07043v3-abstract-full" style="display: none;"> Quantum information scrambling describes the delocalization of local information to global information in the form of entanglement throughout all possible degrees of freedom. A natural measure of scrambling is the tripartite mutual information (TMI), which quantifies the amount of delocalized information for a given quantum channel with its state representation, i.e., the Choi state. In this work, we show that quantum information scrambling can also be witnessed by temporal quantum steering for qubit systems. We can do so because there is a fundamental equivalence between the Choi state and the pseudo-density matrix formalism used in temporal quantum correlations. In particular, we propose a quantity as a scrambling witness, based on a measure of temporal steering called temporal steerable weight. We justify the scrambling witness for unitary qubit channels by proving that the quantity vanishes whenever the channel is non-scrambling. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2003.07043v3-abstract-full').style.display = 'none'; document.getElementById('2003.07043v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 March, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 104, 022614 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2002.08918">arXiv:2002.08918</a> <span> [<a href="https://arxiv.org/pdf/2002.08918">pdf</a>, <a href="https://arxiv.org/format/2002.08918">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Alibaba Cloud Quantum Development Platform: Surface Code Simulations with Crosstalk </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Huang%2C+C">Cupjin Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Ni%2C+X">Xiaotong Ni</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+F">Fang Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Newman%2C+M">Michael Newman</a>, <a href="/search/quant-ph?searchtype=author&query=Ding%2C+D">Dawei Ding</a>, <a href="/search/quant-ph?searchtype=author&query=Gao%2C+X">Xun Gao</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+T">Tenghui Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+H">Hui-Hai Zhao</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+F">Feng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+G">Gengyan Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+C">Chunqing Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+J">Jianxin Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+Y">Yaoyun Shi</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2002.08918v1-abstract-short" style="display: inline;"> We report, in a sequence of notes, our work on the Alibaba Cloud Quantum Development Platform (AC-QDP). AC-QDP provides a set of tools for aiding the development of both quantum computing algorithms and quantum processors, and is powered by a large-scale classical simulator deployed on Alibaba Cloud. In this note, we simulate a distance-3 logical qubit encoded in the 17-qubit surface code using ex… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.08918v1-abstract-full').style.display = 'inline'; document.getElementById('2002.08918v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2002.08918v1-abstract-full" style="display: none;"> We report, in a sequence of notes, our work on the Alibaba Cloud Quantum Development Platform (AC-QDP). AC-QDP provides a set of tools for aiding the development of both quantum computing algorithms and quantum processors, and is powered by a large-scale classical simulator deployed on Alibaba Cloud. In this note, we simulate a distance-3 logical qubit encoded in the 17-qubit surface code using experimental noise parameters for transmon qubits in a planar circuit QED architecture. Our simulation features crosstalk induced by ZZ-interactions. We show that at the current-stage noise levels, crosstalk contributes significantly to the dephasing of the logical qubit. This results in a total phase-flip probability of $\sim 0.6\%$, about $60\%$ higher than expected without considering crosstalk. This indicates that for the code considered, the current noise parameters approach, but do not yet meet, the break-even fault-tolerance regime. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.08918v1-abstract-full').style.display = 'none'; document.getElementById('2002.08918v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">23 pages, 6 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2002.02823">arXiv:2002.02823</a> <span> [<a href="https://arxiv.org/pdf/2002.02823">pdf</a>, <a href="https://arxiv.org/format/2002.02823">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.22331/q-2021-09-28-552">10.22331/q-2021-09-28-552 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Robust self-testing of steerable quantum assemblages and its applications on device-independent quantum certification </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+W">Wenbin Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Tura%2C+J">Jordi Tura</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2002.02823v3-abstract-short" style="display: inline;"> Given a Bell inequality, if its maximal quantum violation can be achieved only by a single set of measurements for each party or a single quantum state, up to local unitaries, one refers to such a phenomenon as self-testing. For instance, the maximal quantum violation of the Clauser-Horne-Shimony-Holt inequality certifies that the underlying state contains the two-qubit maximally entangled state a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.02823v3-abstract-full').style.display = 'inline'; document.getElementById('2002.02823v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2002.02823v3-abstract-full" style="display: none;"> Given a Bell inequality, if its maximal quantum violation can be achieved only by a single set of measurements for each party or a single quantum state, up to local unitaries, one refers to such a phenomenon as self-testing. For instance, the maximal quantum violation of the Clauser-Horne-Shimony-Holt inequality certifies that the underlying state contains the two-qubit maximally entangled state and the measurements of one party contains a pair of anti-commuting qubit observables. As a consequence, the other party automatically verifies the set of states remotely steered, namely the "assemblage", is in the eigenstates of a pair of anti-commuting observables. It is natural to ask if the quantum violation of the Bell inequality is not maximally achieved, or if one does not care about self-testing the state or measurements, are we capable of estimating how close the underlying assemblage is to the reference one? In this work, we provide a systematic device-independent estimation by proposing a framework called "robust self-testing of steerable quantum assemblages". In particular, we consider assemblages violating several paradigmatic Bell inequalities and obtain the robust self-testing statement for each scenario. Our result is device-independent (DI), i.e., no assumption is made on the shared state and the measurement devices involved. Our work thus not only paves a way for exploring the connection between the boundary of quantum set of correlations and steerable assemblages, but also provides a useful tool in the areas of DI quantum certification. As two explicit applications, we show 1) that it can be used for an alternative proof of the protocol of DI certification of all entangled two-qubit states proposed by Bowles et al., and 2) that it can be used to verify all non-entanglement-breaking qubit channels with fewer assumptions compared with the work of Rosset et al. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.02823v3-abstract-full').style.display = 'none'; document.getElementById('2002.02823v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Comments welcome! The MATLAB codes to accompany this work can be found at https://git.io/Jvnmn . v2: A paragraph was added in Discussion Section. v3: Accepted version. Major revision on self-testing complex-valued assemblages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum 5, 552 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.13432">arXiv:1909.13432</a> <span> [<a href="https://arxiv.org/pdf/1909.13432">pdf</a>, <a href="https://arxiv.org/format/1909.13432">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1364/OPTICA.456382">10.1364/OPTICA.456382 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Device-independent verification of Einstein-Podolsky-Rosen steering </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+Y">Yuan-Yuan Zhao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+C">Chao Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Cheng%2C+S">Shuming Cheng</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+X">Xinhui Li</a>, <a href="/search/quant-ph?searchtype=author&query=Guo%2C+Y">Yu Guo</a>, <a href="/search/quant-ph?searchtype=author&query=Liu%2C+B">Bi-Heng Liu</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Wen%2C+Q">Qiaoyan Wen</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+Y">Yun-Feng Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Xiang%2C+G">Guo-Yong Xiang</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+C">Chuan-Feng Li</a>, <a href="/search/quant-ph?searchtype=author&query=Guo%2C+G">Guang-Can Guo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1909.13432v6-abstract-short" style="display: inline;"> Entanglement lies at the heart of quantum mechanics, and has been identified an essential resource for diverse applications in quantum information. If entanglement could be verified without any trust in the devices of observers, i.e., in a device-independent (DI) way, then unconditional security can be guaranteed for various quantum information tasks. In this work, we propose an experimental-frien… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.13432v6-abstract-full').style.display = 'inline'; document.getElementById('1909.13432v6-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.13432v6-abstract-full" style="display: none;"> Entanglement lies at the heart of quantum mechanics, and has been identified an essential resource for diverse applications in quantum information. If entanglement could be verified without any trust in the devices of observers, i.e., in a device-independent (DI) way, then unconditional security can be guaranteed for various quantum information tasks. In this work, we propose an experimental-friendly DI protocol to certify the presence of entanglement, based on Einstein-Podolsky-Rosen (EPR) steering. We first establish the DI verification framework, relying on the measurement-device-independent technique and self-testing, and show it is able to verify all EPR-steerable states. In the context of three-measurement settings as per party, it is found to be noise robustness towards inefficient measurements and imperfect self-testing. Finally, a four-photon experiment is implemented to device-independently verify EPR-steering even for Bell local states. Our work paves the way for realistic implementations of secure quantum information tasks. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.13432v6-abstract-full').style.display = 'none'; document.getElementById('1909.13432v6-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Experiments are rerun to collect more data to do tomography and the text is significantly refined; Comments are still welcome</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Optica 10, 1 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1908.09556">arXiv:1908.09556</a> <span> [<a href="https://arxiv.org/pdf/1908.09556">pdf</a>, <a href="https://arxiv.org/format/1908.09556">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Superconductivity">cond-mat.supr-con</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41534-020-00287-w">10.1038/s41534-020-00287-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Amplitude and frequency sensing of microwave fields with a superconducting transmon qudit </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Kristen%2C+M">Maximilian Kristen</a>, <a href="/search/quant-ph?searchtype=author&query=Schneider%2C+A">Andre Schneider</a>, <a href="/search/quant-ph?searchtype=author&query=Stehli%2C+A">Alexander Stehli</a>, <a href="/search/quant-ph?searchtype=author&query=Wolz%2C+T">Tim Wolz</a>, <a href="/search/quant-ph?searchtype=author&query=Danilin%2C+S">Sergey Danilin</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H+S">Hsiang S. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Long%2C+J">Junling Long</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+X">Xian Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Lake%2C+R+E">Russell E. Lake</a>, <a href="/search/quant-ph?searchtype=author&query=Pappas%2C+D+P">David P. Pappas</a>, <a href="/search/quant-ph?searchtype=author&query=Ustinov%2C+A+V">Alexey V. Ustinov</a>, <a href="/search/quant-ph?searchtype=author&query=Weides%2C+M">Martin Weides</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1908.09556v3-abstract-short" style="display: inline;"> Experiments with superconducting circuits require careful calibration of the applied pulses and fields over a large frequency range. This remains an ongoing challenge as commercial semiconductor electronics are not able to probe signals arriving at the chip due to its cryogenic environment. Here, we demonstrate how the on-chip amplitude and frequency of a microwave signal can be inferred from the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.09556v3-abstract-full').style.display = 'inline'; document.getElementById('1908.09556v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1908.09556v3-abstract-full" style="display: none;"> Experiments with superconducting circuits require careful calibration of the applied pulses and fields over a large frequency range. This remains an ongoing challenge as commercial semiconductor electronics are not able to probe signals arriving at the chip due to its cryogenic environment. Here, we demonstrate how the on-chip amplitude and frequency of a microwave signal can be inferred from the ac Stark shifts of higher transmon levels. In our time-resolved measurements we employ Ramsey fringes, allowing us to detect the amplitude of the systems transfer function over a range of several hundreds of MHz with an energy sensitivity on the order of $10^{-4}$. Combined with similar measurements for the phase of the transfer function, our sensing method can facilitate pulse correction for high fidelity quantum gates in superconducting circuits. Additionally, the potential to characterize arbitrary microwave fields promotes applications in related areas of research, such as quantum optics or hybrid microwave systems including photonic, mechanical or magnonic subsystems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.09556v3-abstract-full').style.display = 'none'; document.getElementById('1908.09556v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 May, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> npj Quantum Inf 6, 57 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.13454">arXiv:1905.13454</a> <span> [<a href="https://arxiv.org/pdf/1905.13454">pdf</a>, <a href="https://arxiv.org/ps/1905.13454">ps</a>, <a href="https://arxiv.org/format/1905.13454">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41534-020-00321-x">10.1038/s41534-020-00321-x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Experimental test of non-macrorealistic cat-states in the cloud </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Lambert%2C+N">Neill Lambert</a>, <a href="/search/quant-ph?searchtype=author&query=Jhan%2C+F">Fong-Ruei Jhan</a>, <a href="/search/quant-ph?searchtype=author&query=Emary%2C+C">Clive Emary</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.13454v2-abstract-short" style="display: inline;"> The Leggett-Garg inequality attempts to classify experimental outcomes as arising from one of two possible classes of physical theories: those described by macrorealism (which obey our intuition about how the macroscopic classical world behaves), and those that are not (e.g., quantum theory). The development of cloud-based quantum computing devices enables us to explore the limits of macrorealism… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.13454v2-abstract-full').style.display = 'inline'; document.getElementById('1905.13454v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.13454v2-abstract-full" style="display: none;"> The Leggett-Garg inequality attempts to classify experimental outcomes as arising from one of two possible classes of physical theories: those described by macrorealism (which obey our intuition about how the macroscopic classical world behaves), and those that are not (e.g., quantum theory). The development of cloud-based quantum computing devices enables us to explore the limits of macrorealism in new regimes. In particular, here we take advantage of the properties of the programmable nature of the IBM quantum experience to observe the violation of the Leggett-Garg inequality (in the form of a ``quantum witness") as a function of the number of constituent systems (qubits), while simultaneously maximizing the `disconnectivity', a potential measure of macroscopicity, between constituents. Our results show that two-qubit and four-qubit ``cat states" (which have large disconnectivity) are seen to violate the inequality, and hence can be classified as nonmacrorealistic. In contrast, a six-qubit cat state does not violate the ``quantum-witness" beyond a so-called clumsy invasive-measurement bound, and thus is compatible with ``clumsy macrorealism". As a comparison, we also consider un-entangled product states with n = 2, 3, 4, and 6 qubits, in which the disconnectivity is low. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.13454v2-abstract-full').style.display = 'none'; document.getElementById('1905.13454v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 7 December, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 31 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> npj Quantum information 6, 98 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.10791">arXiv:1905.10791</a> <span> [<a href="https://arxiv.org/pdf/1905.10791">pdf</a>, <a href="https://arxiv.org/format/1905.10791">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41586-020-2507-2">10.1038/s41586-020-2507-2 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Imaging viscous flow of the Dirac fluid in graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+M+J+H">Mark J. H. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+T+X">Tony X. Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+Q">Qing Li</a>, <a href="/search/quant-ph?searchtype=author&query=Shin%2C+Y+J">Young J. Shin</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+J+K">Jing K. Shi</a>, <a href="/search/quant-ph?searchtype=author&query=Burch%2C+C">Claire Burch</a>, <a href="/search/quant-ph?searchtype=author&query=Anderson%2C+L+E">Laurel E. Anderson</a>, <a href="/search/quant-ph?searchtype=author&query=Pierce%2C+A+T">Andrew T. Pierce</a>, <a href="/search/quant-ph?searchtype=author&query=Xie%2C+Y">Yonglong Xie</a>, <a href="/search/quant-ph?searchtype=author&query=Hamo%2C+A">Assaf Hamo</a>, <a href="/search/quant-ph?searchtype=author&query=Vool%2C+U">Uri Vool</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+H">Huiliang Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Casola%2C+F">Francesco Casola</a>, <a href="/search/quant-ph?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/quant-ph?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/quant-ph?searchtype=author&query=Kim%2C+P">Philip Kim</a>, <a href="/search/quant-ph?searchtype=author&query=Yacoby%2C+A">Amir Yacoby</a>, <a href="/search/quant-ph?searchtype=author&query=Walsworth%2C+R+L">Ronald L. Walsworth</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.10791v3-abstract-short" style="display: inline;"> The electron-hole plasma in charge-neutral graphene is predicted to realize a quantum critical system whose transport features a universal hydrodynamic description, even at room temperature. This quantum critical "Dirac fluid" is expected to have a shear viscosity close to a minimum bound, with an inter-particle scattering rate saturating at the Planckian time $\hbar/(k_B T)$. While electrical tra… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.10791v3-abstract-full').style.display = 'inline'; document.getElementById('1905.10791v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.10791v3-abstract-full" style="display: none;"> The electron-hole plasma in charge-neutral graphene is predicted to realize a quantum critical system whose transport features a universal hydrodynamic description, even at room temperature. This quantum critical "Dirac fluid" is expected to have a shear viscosity close to a minimum bound, with an inter-particle scattering rate saturating at the Planckian time $\hbar/(k_B T)$. While electrical transport measurements at finite carrier density are consistent with hydrodynamic electron flow in graphene, a "smoking gun" of viscous behavior remains elusive. In this work, we directly image viscous Dirac fluid flow in graphene at room temperature via measurement of the associated stray magnetic field. Nanoscale magnetic imaging is performed using quantum spin magnetometers realized with nitrogen vacancy (NV) centers in diamond. Scanning single-spin and wide-field magnetometry reveals a parabolic Poiseuille profile for electron flow in a graphene channel near the charge neutrality point, establishing the viscous transport of the Dirac fluid. This measurement is in contrast to the conventional uniform flow profile imaged in an Ohmic conductor. Via combined imaging-transport measurements, we obtain viscosity and scattering rates, and observe that these quantities are comparable to the universal values expected at quantum criticality. This finding establishes a nearly-ideal electron fluid in neutral graphene at room temperature. Our results pave the way to study hydrodynamic transport in quantum critical fluids relevant to strongly-correlated electrons in high-$T_c$ superconductors. This work also highlights the capability of quantum spin magnetometers to probe correlated-electronic phenomena at the nanoscale. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.10791v3-abstract-full').style.display = 'none'; document.getElementById('1905.10791v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 August, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Author list and title have been updated in published version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 583, 537 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1901.08298">arXiv:1901.08298</a> <span> [<a href="https://arxiv.org/pdf/1901.08298">pdf</a>, <a href="https://arxiv.org/format/1901.08298">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41534-020-00307-9">10.1038/s41534-020-00307-9 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Experimental demonstration of measurement-device-independent measure of quantum steering </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zhao%2C+Y">Yuan-Yuan Zhao</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+H">Hong-Bin Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a>, <a href="/search/quant-ph?searchtype=author&query=Xiang%2C+G">Guo-Yong Xiang</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+C">Chuan-Feng Li</a>, <a href="/search/quant-ph?searchtype=author&query=Guo%2C+G">Guang-Can Guo</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1901.08298v2-abstract-short" style="display: inline;"> Within the framework of quantum refereed steering games, quantum steerability can be certified without any assumption on the underlying state nor the measurements involved. Such a scheme is termed the measurement-device-independent (MDI) scenario. Here we introduce a measure of steerability in an MDI scenario, i.e., the result merely depends on the observed statistics and the quantum inputs. We pr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1901.08298v2-abstract-full').style.display = 'inline'; document.getElementById('1901.08298v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1901.08298v2-abstract-full" style="display: none;"> Within the framework of quantum refereed steering games, quantum steerability can be certified without any assumption on the underlying state nor the measurements involved. Such a scheme is termed the measurement-device-independent (MDI) scenario. Here we introduce a measure of steerability in an MDI scenario, i.e., the result merely depends on the observed statistics and the quantum inputs. We prove that such a measure satisfies the convex steering monotone. Moreover, it is robust against not only measurement biases but also losses. We also experimentally estimate the amount of the measure with an entangled photon source. As two by-products, our experimental results provide lower bounds on an entanglement measure of the underlying state and an incompatible measure of the involved measurement. Our research paves a way for exploring one-side device-independent quantum information processing within an MDI framework. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1901.08298v2-abstract-full').style.display = 'none'; document.getElementById('1901.08298v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 January, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">v2:10 pages, 3 figures, published version. This version combines the previous version with the theoretical work [arXiv:1807.08901]. v1:11 pages, 3 figures. Comments welcome!</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> npj Quantum Inf 6, 77 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1809.11048">arXiv:1809.11048</a> <span> [<a href="https://arxiv.org/pdf/1809.11048">pdf</a>, <a href="https://arxiv.org/format/1809.11048">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.5063252">10.1063/1.5063252 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Kinetic Inductance Traveling Wave Amplifiers For Multiplexed Qubit Readout </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ranzani%2C+L">Leonardo Ranzani</a>, <a href="/search/quant-ph?searchtype=author&query=Bal%2C+M">Mustafa Bal</a>, <a href="/search/quant-ph?searchtype=author&query=Fong%2C+K+C">Kin Chung Fong</a>, <a href="/search/quant-ph?searchtype=author&query=Ribeill%2C+G">Guilhem Ribeill</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+X">Xian Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Long%2C+J">Junling Long</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H+S">Hsiang Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Erickson%2C+R+P">Robert P. Erickson</a>, <a href="/search/quant-ph?searchtype=author&query=Pappas%2C+D">David Pappas</a>, <a href="/search/quant-ph?searchtype=author&query=Ohki%2C+T+A">Thomas A. Ohki</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1809.11048v2-abstract-short" style="display: inline;"> We describe a kinetic inductance traveling-wave (KIT) amplifier suitable for superconducting quantum information measurements and characterize its wideband scattering and noise properties. We use mechanical microwave switches to calibrate the four amplifier scattering parameters up to the device input and output connectors at the dilution refrigerator base temperature and a tunable temperature loa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1809.11048v2-abstract-full').style.display = 'inline'; document.getElementById('1809.11048v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1809.11048v2-abstract-full" style="display: none;"> We describe a kinetic inductance traveling-wave (KIT) amplifier suitable for superconducting quantum information measurements and characterize its wideband scattering and noise properties. We use mechanical microwave switches to calibrate the four amplifier scattering parameters up to the device input and output connectors at the dilution refrigerator base temperature and a tunable temperature load to characterize the amplifier noise. Finally, we demonstrate the high fidelity simultaneous dispersive readout of two superconducting transmon qubits. The KIT amplifier provides low-noise amplification of both readout tones with readout fidelities of 83% and 89% and negligible effect on qubit lifetime and coherence. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1809.11048v2-abstract-full').style.display = 'none'; document.getElementById('1809.11048v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 November, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 September, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 5 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1807.08901">arXiv:1807.08901</a> <span> [<a href="https://arxiv.org/pdf/1807.08901">pdf</a>, <a href="https://arxiv.org/ps/1807.08901">ps</a>, <a href="https://arxiv.org/format/1807.08901">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Measurement-device-independent measure of steerability and witnesses for all steerable resources </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+H">Hong-Bin Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1807.08901v2-abstract-short" style="display: inline;"> The fact that nonlocality implies steering enables one to certify steerability by using a Bell inequality violation. Such a certification is device-independent (DI), i.e., one makes no assumption neither on the underlying state nor on the measurements. However, not all steerable states can violate a Bell inequality. Here, we systematically construct a collection of witnesses for steerable resource… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.08901v2-abstract-full').style.display = 'inline'; document.getElementById('1807.08901v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1807.08901v2-abstract-full" style="display: none;"> The fact that nonlocality implies steering enables one to certify steerability by using a Bell inequality violation. Such a certification is device-independent (DI), i.e., one makes no assumption neither on the underlying state nor on the measurements. However, not all steerable states can violate a Bell inequality. Here, we systematically construct a collection of witnesses for steerable resources, defined by assemblages, in a measurement-device-independent (MDI) scenario. The inputs driving the measurement are replaced by a set of tomographically complete quantum states, and neither the detectors nor the underlying state is characterized. We show that all steerable assemblages can be detected by properly chosen witnesses. Furthermore, we introduce the first measure of steerability in an MDI scenario and show that such a measure is a standard one, i.e., a steering monotone, by proving that it is equivalent to the steering robustness. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.08901v2-abstract-full').style.display = 'none'; document.getElementById('1807.08901v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 April, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 July, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 2 figures, comments welcome</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1805.08445">arXiv:1805.08445</a> <span> [<a href="https://arxiv.org/pdf/1805.08445">pdf</a>, <a href="https://arxiv.org/format/1805.08445">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.98.043803">10.1103/PhysRevA.98.043803 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing higher-order transitions through scattering of microwave photons in the ultrastrong-coupling regime of circuit QED </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Chen%2C+G">Guan-Ting Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Kuo%2C+P">Po-Chen Kuo</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+G">Guang-Yin Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1805.08445v1-abstract-short" style="display: inline;"> Higher-order transitions can occur in the ultrastrong-coupling regime of circuit QED through virtual processes governed by the counter-rotating interactions. We propose a feasible way to probe higher-order transitions through the scattering of propagating microwave photons incident on the hybrid qubit-cavity system. The lineshapes in the scattering spectra can indicate the coherent interaction bet… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.08445v1-abstract-full').style.display = 'inline'; document.getElementById('1805.08445v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1805.08445v1-abstract-full" style="display: none;"> Higher-order transitions can occur in the ultrastrong-coupling regime of circuit QED through virtual processes governed by the counter-rotating interactions. We propose a feasible way to probe higher-order transitions through the scattering of propagating microwave photons incident on the hybrid qubit-cavity system. The lineshapes in the scattering spectra can indicate the coherent interaction between the qubits and the cavity, and the higher-order transitions can be identified in the population spectra. We further find that if the coupling strengths between the two qubits and the cavity are tuned to be asymmetric, the dark antisymmetric state with the Fano-lineshape can also be detected from the variations in the scattering spectra. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.08445v1-abstract-full').style.display = 'none'; document.getElementById('1805.08445v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 May, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 98, 043803 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1710.11387">arXiv:1710.11387</a> <span> [<a href="https://arxiv.org/pdf/1710.11387">pdf</a>, <a href="https://arxiv.org/ps/1710.11387">ps</a>, <a href="https://arxiv.org/format/1710.11387">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.98.022104">10.1103/PhysRevA.98.022104 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Hierarchy in temporal quantum correlations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Lambert%2C+N">Neill Lambert</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1710.11387v3-abstract-short" style="display: inline;"> Einstein-Podolsky-Rosen (EPR) steering is an intermediate quantum correlation that lies in between entanglement and Bell non-locality. Its temporal analogue, temporal steering, has recently been shown to have applications in quantum information and open quantum systems. Here, we show that there exists a hierarchy among the three temporal quantum correlations: temporal inseparability, temporal stee… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1710.11387v3-abstract-full').style.display = 'inline'; document.getElementById('1710.11387v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1710.11387v3-abstract-full" style="display: none;"> Einstein-Podolsky-Rosen (EPR) steering is an intermediate quantum correlation that lies in between entanglement and Bell non-locality. Its temporal analogue, temporal steering, has recently been shown to have applications in quantum information and open quantum systems. Here, we show that there exists a hierarchy among the three temporal quantum correlations: temporal inseparability, temporal steering, and macrorealism. Given that the temporal inseparability can be used to define a measure of quantum causality, similarly the quantification of temporal steering can be viewed as a weaker measure of direct cause and can be used to distinguish between direct cause and common cause in a quantum network. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1710.11387v3-abstract-full').style.display = 'none'; document.getElementById('1710.11387v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 August, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 31 October, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 98, 022104 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1709.06703">arXiv:1709.06703</a> <span> [<a href="https://arxiv.org/pdf/1709.06703">pdf</a>, <a href="https://arxiv.org/format/1709.06703">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.97.022338">10.1103/PhysRevA.97.022338 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Einstein-Podolsky-Rosen steering: Its geometric quantification and witness </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Budroni%2C+C">Costantino Budroni</a>, <a href="/search/quant-ph?searchtype=author&query=Miranowicz%2C+A">Adam Miranowicz</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1709.06703v4-abstract-short" style="display: inline;"> We propose a measure of quantum steerability, namely a convex steering monotone, based on the trace distance between a given assemblage and its corresponding closest assemblage admitting a local-hidden-state (LHS) model. We provide methods to estimate such a quantity, via lower and upper bounds, based on semidefinite programming. One of these upper bounds has a clear geometrical interpretation as… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1709.06703v4-abstract-full').style.display = 'inline'; document.getElementById('1709.06703v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1709.06703v4-abstract-full" style="display: none;"> We propose a measure of quantum steerability, namely a convex steering monotone, based on the trace distance between a given assemblage and its corresponding closest assemblage admitting a local-hidden-state (LHS) model. We provide methods to estimate such a quantity, via lower and upper bounds, based on semidefinite programming. One of these upper bounds has a clear geometrical interpretation as a linear function of rescaled Euclidean distances in the Bloch sphere between the normalized quantum states of: (i) a given assemblage and (ii) an LHS assemblage. For a qubit-qubit quantum state, the above ideas also allow us to visualize various steerability properties of the state in the Bloch sphere via the so-called LHS surface. In particular, some steerability properties can be obtained by comparing such an LHS surface with a corresponding quantum steering ellipsoid. Thus, we propose a witness of steerability corresponding to the difference of the volumes enclosed by these two surfaces. This witness (which reveals the steerability of a quantum state) enables finding an optimal measurement basis, which can then be used to determine the proposed steering monotone (which describes the steerability of an assemblage) optimized over all mutually-unbiased bases. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1709.06703v4-abstract-full').style.display = 'none'; document.getElementById('1709.06703v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 March, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 September, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 97, 022338 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1705.08993">arXiv:1705.08993</a> <span> [<a href="https://arxiv.org/pdf/1705.08993">pdf</a>, <a href="https://arxiv.org/format/1705.08993">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Superconductivity">cond-mat.supr-con</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.4993937">10.1063/1.4993937 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Overlap junctions for high coherence superconducting qubits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Wu%2C+X">X. Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Long%2C+J+L">J. L. Long</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H+S">H. S. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Lake%2C+R+E">R. E. Lake</a>, <a href="/search/quant-ph?searchtype=author&query=Bal%2C+M">M. Bal</a>, <a href="/search/quant-ph?searchtype=author&query=Pappas%2C+D+P">D. P. Pappas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1705.08993v1-abstract-short" style="display: inline;"> Fabrication of sub-micron Josephson junctions is demonstrated using standard processing techniques for high-coherence, superconducting qubits. These junctions are made in two separate lithography steps with normal-angle evaporation. Most significantly, this work demonstrates that it is possible to achieve high coherence with junctions formed on aluminum surfaces cleaned in situ with Ar milling bef… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.08993v1-abstract-full').style.display = 'inline'; document.getElementById('1705.08993v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1705.08993v1-abstract-full" style="display: none;"> Fabrication of sub-micron Josephson junctions is demonstrated using standard processing techniques for high-coherence, superconducting qubits. These junctions are made in two separate lithography steps with normal-angle evaporation. Most significantly, this work demonstrates that it is possible to achieve high coherence with junctions formed on aluminum surfaces cleaned in situ with Ar milling before the junction oxidation. This method eliminates the angle-dependent shadow masks typically used for small junctions. Therefore, this is conducive to the implementation of typical methods for improving margins and yield using conventional CMOS processing. The current method uses electron-beam lithography and an additive process to define the top and bottom electrodes. Extension of this work to optical lithography and subtractive processes is discussed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.08993v1-abstract-full').style.display = 'none'; document.getElementById('1705.08993v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 May, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages, 3 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1704.08777">arXiv:1704.08777</a> <span> [<a href="https://arxiv.org/pdf/1704.08777">pdf</a>, <a href="https://arxiv.org/ps/1704.08777">ps</a>, <a href="https://arxiv.org/format/1704.08777">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.120.083602">10.1103/PhysRevLett.120.083602 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Electromagnetically induced transparency in circuit QED with nested polariton states </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Long%2C+J">Junling Long</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H+S">H. S. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+X">Xian Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Gu%2C+X">Xiu Gu</a>, <a href="/search/quant-ph?searchtype=author&query=Lake%2C+R+E">Russell E. Lake</a>, <a href="/search/quant-ph?searchtype=author&query=Bal%2C+M">Mustafa Bal</a>, <a href="/search/quant-ph?searchtype=author&query=Liu%2C+Y">Yu-xi Liu</a>, <a href="/search/quant-ph?searchtype=author&query=Pappas%2C+D+P">David P. Pappas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1704.08777v2-abstract-short" style="display: inline;"> Electromagnetically induced transparency (EIT) is a signature of quantum interference in an atomic three-level system. By driving the dressed cavity-qubit states of a two-dimensional circuit QED system, we generate a set of polariton states in the nesting regime. The lowest three energy levels are utilized to form the $螞$-type system. EIT is observed and verified by Akaike's information criterion… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1704.08777v2-abstract-full').style.display = 'inline'; document.getElementById('1704.08777v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1704.08777v2-abstract-full" style="display: none;"> Electromagnetically induced transparency (EIT) is a signature of quantum interference in an atomic three-level system. By driving the dressed cavity-qubit states of a two-dimensional circuit QED system, we generate a set of polariton states in the nesting regime. The lowest three energy levels are utilized to form the $螞$-type system. EIT is observed and verified by Akaike's information criterion based testing. Negative group velocities up to $-0.52\pm0.09$ km/s are obtained based on the dispersion relation in the EIT transmission spectrum. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1704.08777v2-abstract-full').style.display = 'none'; document.getElementById('1704.08777v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 February, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 April, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Lett. 120, 083602 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1704.00803">arXiv:1704.00803</a> <span> [<a href="https://arxiv.org/pdf/1704.00803">pdf</a>, <a href="https://arxiv.org/ps/1704.00803">ps</a>, <a href="https://arxiv.org/format/1704.00803">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.96.042339">10.1103/PhysRevA.96.042339 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Qubit gates using hyperbolic secant pulses </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H+S">H. S. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Long%2C+J+L">J. L. Long</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+X">X. Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Bal%2C+M">M. Bal</a>, <a href="/search/quant-ph?searchtype=author&query=Lake%2C+R+E">R. E. Lake</a>, <a href="/search/quant-ph?searchtype=author&query=Barnes%2C+E">Edwin Barnes</a>, <a href="/search/quant-ph?searchtype=author&query=Economou%2C+S+E">Sophia E. Economou</a>, <a href="/search/quant-ph?searchtype=author&query=Pappas%2C+D+P">D. P. Pappas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1704.00803v2-abstract-short" style="display: inline;"> It has been known since the early days of quantum mechanics that hyperbolic secant pulses possess the unique property that they can perform cyclic evolution on two-level quantum systems independently of the pulse detuning. More recently, it was realized that they induce detuning- controlled phases without changing state populations. Here, we experimentally demonstrate the properties of hyperbolic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1704.00803v2-abstract-full').style.display = 'inline'; document.getElementById('1704.00803v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1704.00803v2-abstract-full" style="display: none;"> It has been known since the early days of quantum mechanics that hyperbolic secant pulses possess the unique property that they can perform cyclic evolution on two-level quantum systems independently of the pulse detuning. More recently, it was realized that they induce detuning- controlled phases without changing state populations. Here, we experimentally demonstrate the properties of hyperbolic secant pulses on superconducting transmon qubits and contrast them with the more commonly used Gaussian and square waves. We further show that these properties can be exploited to implement phase gates, nominally without exiting the computational subspace. This enables us to demonstrate the first microwave-driven Z-gates with a single control parameter, the detuning. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1704.00803v2-abstract-full').style.display = 'none'; document.getElementById('1704.00803v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 April, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 3 April, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 6 figures, added supplementary information</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 96, 042339 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1610.05490">arXiv:1610.05490</a> <span> [<a href="https://arxiv.org/pdf/1610.05490">pdf</a>, <a href="https://arxiv.org/ps/1610.05490">ps</a>, <a href="https://arxiv.org/format/1610.05490">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.94.062126">10.1103/PhysRevA.94.062126 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Temporal Steering in Four Dimensions with applications to coupled qubits and magnetoreception </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Huan-Yu Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+S">Shin-Liang Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+H">Hong-Bin Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Lambert%2C+N">Neill Lambert</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+Y">Yueh-Nan Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1610.05490v2-abstract-short" style="display: inline;"> Einstein-Podolsky-Rosen (EPR) steering allows Alice to remotely prepare a state in some specific bases for Bob through her choice of measurements. The temporal analogue of EPR steering, temporal steering, also reveals the steerability of a single system between different times. Focusing on a four-dimensional system, here we investigate the dynamics of the temporal steering measures, the temporal s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.05490v2-abstract-full').style.display = 'inline'; document.getElementById('1610.05490v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1610.05490v2-abstract-full" style="display: none;"> Einstein-Podolsky-Rosen (EPR) steering allows Alice to remotely prepare a state in some specific bases for Bob through her choice of measurements. The temporal analogue of EPR steering, temporal steering, also reveals the steerability of a single system between different times. Focusing on a four-dimensional system, here we investigate the dynamics of the temporal steering measures, the temporal steering robustness, using 5 mutually unbiased bases. As an example of an application, we use these measures to examine the temporal correlations in a radical pair model of magnetoreception. We find that, due to interactions with a static nuclear spin, the radical pair model exhibits strong non-Markovianity. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.05490v2-abstract-full').style.display = 'none'; document.getElementById('1610.05490v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 January, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 October, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 94, 062126 (2016) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1509.09280">arXiv:1509.09280</a> <span> [<a href="https://arxiv.org/pdf/1509.09280">pdf</a>, <a href="https://arxiv.org/format/1509.09280">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Superconductivity">cond-mat.supr-con</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.4937922">10.1063/1.4937922 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Low-noise kinetic inductance traveling-wave amplifier using three-wave mixing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Vissers%2C+M+R">Michael R. Vissers</a>, <a href="/search/quant-ph?searchtype=author&query=Erickson%2C+R+P">Robert P. Erickson</a>, <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H">Hsiang-Sheng Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Vale%2C+L">Leila Vale</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+X">Xian Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Hilton%2C+G">Gene Hilton</a>, <a href="/search/quant-ph?searchtype=author&query=Pappas%2C+D+P">David P. Pappas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1509.09280v1-abstract-short" style="display: inline;"> We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone we are able to generate parametric amplification using three-wave mixing. The devices exhibit gain of more… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1509.09280v1-abstract-full').style.display = 'inline'; document.getElementById('1509.09280v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1509.09280v1-abstract-full" style="display: none;"> We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone we are able to generate parametric amplification using three-wave mixing. The devices exhibit gain of more than 15 dB across an instantaneous bandwidth from 4 to 8 GHz. The total usable gain bandwidth, including both sides of the signal-idler gain region, is more than 6 GHz. The noise referred to the input of the devices approaches the quantum limit, with less than 1 photon excess noise. Compared to similarly constructed four-wave mixing amplifiers, these devices operate with the RF pump at $\sim$20 dB lower power and at frequencies far from the signal. This will permit easier integration into large scale qubit and detector applications. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1509.09280v1-abstract-full').style.display = 'none'; document.getElementById('1509.09280v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 September, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2015. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1502.03884">arXiv:1502.03884</a> <span> [<a href="https://arxiv.org/pdf/1502.03884">pdf</a>, <a href="https://arxiv.org/ps/1502.03884">ps</a>, <a href="https://arxiv.org/format/1502.03884">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.91.042305">10.1103/PhysRevA.91.042305 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Generating and verifying entangled itinerant microwave fields with efficient and independent measurements </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ku%2C+H+S">H. S. Ku</a>, <a href="/search/quant-ph?searchtype=author&query=Kindel%2C+W+F">W. F. Kindel</a>, <a href="/search/quant-ph?searchtype=author&query=Mallet%2C+F">F. Mallet</a>, <a href="/search/quant-ph?searchtype=author&query=Glancy%2C+S">S. Glancy</a>, <a href="/search/quant-ph?searchtype=author&query=Irwin%2C+K+D">K. D. Irwin</a>, <a href="/search/quant-ph?searchtype=author&query=Hilton%2C+G+C">G. C. Hilton</a>, <a href="/search/quant-ph?searchtype=author&query=Vale%2C+L+R">L. R. Vale</a>, <a href="/search/quant-ph?searchtype=author&query=Lehnert%2C+K+W">K. W. Lehnert</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1502.03884v1-abstract-short" style="display: inline;"> By combining a squeezed propagating microwave field and an unsqueezed vacuum field on a hybrid (microwave beam-splitter), we generate entanglement between the two output modes. We verify that we have generated entangled states by making independent and efficient single-quadrature measurements of the two output modes. We observe the entanglement witness $E_\mathrm{W}=-0.263^{+0.001}_{-0.036}$ and t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.03884v1-abstract-full').style.display = 'inline'; document.getElementById('1502.03884v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1502.03884v1-abstract-full" style="display: none;"> By combining a squeezed propagating microwave field and an unsqueezed vacuum field on a hybrid (microwave beam-splitter), we generate entanglement between the two output modes. We verify that we have generated entangled states by making independent and efficient single-quadrature measurements of the two output modes. We observe the entanglement witness $E_\mathrm{W}=-0.263^{+0.001}_{-0.036}$ and the negativity $N=0.0824^{+0.01}_{-0.0004}$ with measurement efficiencies at least $26\pm{0.1}\%$ and $41\pm{0.2}\%$ for channel~1 and 2 respectively. These measurements show that the output two-mode state violates the separability criterion and therefore demonstrate entanglement. This shared entanglement between propagating microwaves provides an important resource for building quantum networks with superconducting microwave systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.03884v1-abstract-full').style.display = 'none'; document.getElementById('1502.03884v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 February, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2015. </p> </li> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Ku%2C+H&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Ku%2C+H&start=0" 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