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<button class="button is-small 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=Zeng%2C+J&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Zeng%2C+J&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Zeng%2C+J&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/2501.15341">arXiv:2501.15341</a> <span> [<a href="https://arxiv.org/pdf/2501.15341">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"> Generation of narrowband quantum emitters in hBN with optically addressable spins </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Whitefield%2C+B">Benjamin Whitefield</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+H+Z+J">Helen Zhi Jie Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Liddle-Wesolowski%2C+J">James Liddle-Wesolowski</a>, <a href="/search/quant-ph?searchtype=author&query=Robertson%2C+I+O">Islay O. Robertson</a>, <a href="/search/quant-ph?searchtype=author&query=Iv%C3%A1dy%2C+V">Viktor Iv谩dy</a>, <a href="/search/quant-ph?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/quant-ph?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/quant-ph?searchtype=author&query=Toth%2C+M">Milos Toth</a>, <a href="/search/quant-ph?searchtype=author&query=Tetienne%2C+J">Jean-Philippe Tetienne</a>, <a href="/search/quant-ph?searchtype=author&query=Aharonovich%2C+I">Igor Aharonovich</a>, <a href="/search/quant-ph?searchtype=author&query=Kianinia%2C+M">Mehran Kianinia</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="2501.15341v1-abstract-short" style="display: inline;"> Electron spins coupled with optical transitions in solids stand out as a promising platform for developing spin-based quantum technologies. Recently, hexagonal boron nitride (hBN) - a layered Van der Waals (vdW) crystal, has emerged as a promising host for optically addressable spin systems. However, to date, on-demand generation of isolated single photon emitters with pre-determined spin transiti… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.15341v1-abstract-full').style.display = 'inline'; document.getElementById('2501.15341v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2501.15341v1-abstract-full" style="display: none;"> Electron spins coupled with optical transitions in solids stand out as a promising platform for developing spin-based quantum technologies. Recently, hexagonal boron nitride (hBN) - a layered Van der Waals (vdW) crystal, has emerged as a promising host for optically addressable spin systems. However, to date, on-demand generation of isolated single photon emitters with pre-determined spin transitions has remained elusive. Here, we report on a single step, thermal processing of hBN flakes that produces high density, narrowband, quantum emitters with optically active spin transitions. Remarkably, over 25% of the emitters exhibit a clear signature of an optical spin readout at room temperature, surpassing all previously reported results by an order of magnitude. The generated spin defect complexes exhibit both S = 1 and S = 1/2 transitions, which are explained by charge transfer from strongly to weakly coupled spin pairs. Our work advances the understanding of spin complexes in hBN and paves the way for single spin - photon interfaces in layered vdW materials with applications in quantum sensing and information processing. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.15341v1-abstract-full').style.display = 'none'; document.getElementById('2501.15341v1-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 January, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2409.15302">arXiv:2409.15302</a> <span> [<a href="https://arxiv.org/pdf/2409.15302">pdf</a>, <a href="https://arxiv.org/format/2409.15302">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"> Towards violations of Local Friendliness with quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Labib%2C+F">Farrokh Labib</a>, <a href="/search/quant-ph?searchtype=author&query=Russo%2C+V">Vincent Russo</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="2409.15302v1-abstract-short" style="display: inline;"> Local Friendliness (LF) inequalities follow from seemingly reasonable assumptions about reality: (i) ``absoluteness of observed events'' (e.g., every observed event happens for all observers) and (ii) ``local agency'' (e.g., free choices can be made uncorrelated with other events outside their future light cone). Extended Wigner's Friend Scenario (EWFS) thought experiments show that textbook quant… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.15302v1-abstract-full').style.display = 'inline'; document.getElementById('2409.15302v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2409.15302v1-abstract-full" style="display: none;"> Local Friendliness (LF) inequalities follow from seemingly reasonable assumptions about reality: (i) ``absoluteness of observed events'' (e.g., every observed event happens for all observers) and (ii) ``local agency'' (e.g., free choices can be made uncorrelated with other events outside their future light cone). Extended Wigner's Friend Scenario (EWFS) thought experiments show that textbook quantum mechanics violates these inequalities. Thus, experimental evidence of these violations would make these two assumptions incompatible. In [Nature Physics 16, 1199 (2020)], the authors experimentally implemented an EWFS, using a photonic qubit to play the role of each of the ``friends'' and measured violations of LF. One may question whether a photonic qubit is a physical system that counts as an ``observer'' and thereby question whether the experiment's outcome is significant. Intending to measure increasingly meaningful violations, we propose using a statistical measure called the ``branch factor'' to quantify the ``observerness'' of the system. We then encode the EWFS as a quantum circuit such that the components of the circuit that define the friend are quantum systems of increasing branch factor. We run this circuit on quantum simulators and hardware devices, observing LF violations as the system sizes scale. As errors in quantum computers reduce the significance of the violations, better quantum computers can produce better violations. Our results extend the state of the art in proof-of-concept experimental violations from branch factor 0.0 to branch factor 16.0. This is an initial result in an experimental program for measuring LF violations at increasingly meaningful branch factors using increasingly more powerful quantum processors and networks. We introduce this program as a fundamental science application for near-term and developing quantum technology. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.15302v1-abstract-full').style.display = 'none'; document.getElementById('2409.15302v1-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> 4 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">26 pages, 13 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/2408.07936">arXiv:2408.07936</a> <span> [<a href="https://arxiv.org/pdf/2408.07936">pdf</a>, <a href="https://arxiv.org/format/2408.07936">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="Mathematical Physics">math-ph</span> </div> </div> <p class="title is-5 mathjax"> A quantum-classical hybrid algorithm with Ising model for the learning with errors problem </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zheng%2C+M">Muxi Zheng</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jinfeng Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Yang%2C+W">Wentao Yang</a>, <a href="/search/quant-ph?searchtype=author&query=Chang%2C+P">Pei-Jie Chang</a>, <a href="/search/quant-ph?searchtype=author&query=Yan%2C+B">Bao Yan</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+H">Haoran Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+M">Min Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Wei%2C+S">Shijie Wei</a>, <a href="/search/quant-ph?searchtype=author&query=Long%2C+G">Gui-Lu Long</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="2408.07936v1-abstract-short" style="display: inline;"> The Learning-With-Errors (LWE) problem is a crucial computational challenge with significant implications for post-quantum cryptography and computational learning theory. Here we propose a quantum-classical hybrid algorithm with Ising model (HAWI) to address the LWE problem. Our approach involves transforming the LWE problem into the Shortest Vector Problem (SVP), using variable qubits to encode l… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.07936v1-abstract-full').style.display = 'inline'; document.getElementById('2408.07936v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.07936v1-abstract-full" style="display: none;"> The Learning-With-Errors (LWE) problem is a crucial computational challenge with significant implications for post-quantum cryptography and computational learning theory. Here we propose a quantum-classical hybrid algorithm with Ising model (HAWI) to address the LWE problem. Our approach involves transforming the LWE problem into the Shortest Vector Problem (SVP), using variable qubits to encode lattice vectors into an Ising Hamiltonian. We then identify the low-energy levels of the Hamiltonian to extract the solution, making it suitable for implementation on current noisy intermediate-scale quantum (NISQ) devices. We prove that the number of qubits required is less than $m(3m-1)/2$, where $m$ is the number of samples in the algorithm. Our algorithm is heuristic, and its time complexity depends on the specific quantum algorithm employed to find the Hamiltonian's low-energy levels. If the Quantum Approximate Optimization Algorithm (QAOA) is used to solve the Ising Hamiltonian problem, and the number of iterations satisfies $y < O\left(m\log m\cdot 2^{0.2972k}/pk^2\right)$, our algorithm will outperform the classical Block Korkine-Zolotarev (BKZ) algorithm, where $k$ is the block size related to problem parameters, and $p$ is the number of layers in QAOA. We demonstrate the algorithm by solving a $2$-dimensional LWE problem on a real quantum device with $5$ qubits, showing its potential for solving meaningful instances of the LWE problem in the NISQ era. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.07936v1-abstract-full').style.display = 'none'; document.getElementById('2408.07936v1-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 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.06001">arXiv:2408.06001</a> <span> [<a href="https://arxiv.org/pdf/2408.06001">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Optics">physics.optics</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"> Quantum Efficiency the B-centre in hexagonal boron nitride </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Yamamura%2C+K">Karin Yamamura</a>, <a href="/search/quant-ph?searchtype=author&query=Coste%2C+N">Nathan Coste</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+H+Z+J">Helen Zhi Jie Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Toth%2C+M">Milos Toth</a>, <a href="/search/quant-ph?searchtype=author&query=Kianinia%2C+M">Mehran Kianinia</a>, <a href="/search/quant-ph?searchtype=author&query=Aharonovich%2C+I">Igor Aharonovich</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="2408.06001v1-abstract-short" style="display: inline;"> B-centres in hexagonal boron nitride (hBN) are gaining significant research interest for quantum photonics applications due to precise emitter positioning and highly reproducible emission wavelengths. Here, we leverage the layered nature of hBN to directly measure the quantum efficiency (QE) of single B-centres. The defects were engineered in a 35 nm flake of hBN using electron beam irradiation, a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.06001v1-abstract-full').style.display = 'inline'; document.getElementById('2408.06001v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.06001v1-abstract-full" style="display: none;"> B-centres in hexagonal boron nitride (hBN) are gaining significant research interest for quantum photonics applications due to precise emitter positioning and highly reproducible emission wavelengths. Here, we leverage the layered nature of hBN to directly measure the quantum efficiency (QE) of single B-centres. The defects were engineered in a 35 nm flake of hBN using electron beam irradiation, and the local dielectric environment was altered by transferring a 250 nm hBN flake on top of the one containing the emitters. By analysing the resulting change in measured lifetimes, we determined the QE of B-centres in the thin flake of hBN, as well as after the transfer. Our results indicate that B-centres located in thin flakes can exhibit QEs higher than 40%. Near-unity QEs are achievable under reasonable Purcell enhancement for emitters embedded in thick flakes of hBN, highlighting their promise for quantum photonics applications. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.06001v1-abstract-full').style.display = 'none'; document.getElementById('2408.06001v1-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> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.03543">arXiv:2408.03543</a> <span> [<a href="https://arxiv.org/pdf/2408.03543">pdf</a>, <a href="https://arxiv.org/ps/2408.03543">ps</a>, <a href="https://arxiv.org/format/2408.03543">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.110.062219">10.1103/PhysRevA.110.062219 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Classical-quantum correspondence in the noise-based dissipative systems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jiarui Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+G">Guo-Hao Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+W">Weijie Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Yao%2C+Y">Yao Yao</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="2408.03543v1-abstract-short" style="display: inline;"> We investigate the correspondence between classical noise and quantum environments. Although it has been known that the classical noise can be mapped to the quantum environments only for pure dephasing and infinite-temperature dissipation processes, we describe that this limitation can be circumvented by introducing auxiliary systems and conservation. Taking a two-level system as an example, we co… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.03543v1-abstract-full').style.display = 'inline'; document.getElementById('2408.03543v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.03543v1-abstract-full" style="display: none;"> We investigate the correspondence between classical noise and quantum environments. Although it has been known that the classical noise can be mapped to the quantum environments only for pure dephasing and infinite-temperature dissipation processes, we describe that this limitation can be circumvented by introducing auxiliary systems and conservation. Taking a two-level system as an example, we construct the so-called central spin model with its couplings fluctuating as the classical noise, and then acquire its statistical-average dynamics which captures the dissipations beyond the infinite temperature. By adjusting the number of the auxiliary systems and their initial states, the noise-based model reproduces both Markovian and non-Markovian evolutions. It is also found that different quantities of the two-level system are governed by different model parameters, indicating that the constructed model is an efficient simulator for specific observables, rather than an equivalent form of a realistic open system. In addition, the model is also applicable to investigate topical mechanisms of the open systems, e.g. negative temperatures and asymmetric equidistant quenches. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.03543v1-abstract-full').style.display = 'none'; document.getElementById('2408.03543v1-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 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">8 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/2405.14697">arXiv:2405.14697</a> <span> [<a href="https://arxiv.org/pdf/2405.14697">pdf</a>, <a href="https://arxiv.org/format/2405.14697">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"> Quantum amplitude estimation from classical signal processing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Labib%2C+F">Farrokh Labib</a>, <a href="/search/quant-ph?searchtype=author&query=Clader%2C+B+D">B. David Clader</a>, <a href="/search/quant-ph?searchtype=author&query=Stamatopoulos%2C+N">Nikitas Stamatopoulos</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2405.14697v1-abstract-short" style="display: inline;"> We demonstrate that the problem of amplitude estimation, a core subroutine used in many quantum algorithms, can be mapped directly to a problem in signal processing called direction of arrival (DOA) estimation. The DOA task is to determine the direction of arrival of an incoming wave with the fewest possible measurements. The connection between amplitude estimation and DOA allows us to make use of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.14697v1-abstract-full').style.display = 'inline'; document.getElementById('2405.14697v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.14697v1-abstract-full" style="display: none;"> We demonstrate that the problem of amplitude estimation, a core subroutine used in many quantum algorithms, can be mapped directly to a problem in signal processing called direction of arrival (DOA) estimation. The DOA task is to determine the direction of arrival of an incoming wave with the fewest possible measurements. The connection between amplitude estimation and DOA allows us to make use of the vast amount of signal processing algorithms to post-process the measurements of the Grover iterator at predefined depths. Using an off-the-shelf DOA algorithm called ESPRIT together with a compressed-sensing based sampling approach, we create a phase-estimation free, parallel quantum amplitude estimation (QAE) algorithm with a total query complexity of $\sim 4.9/\varepsilon$ and a parallel query complexity of $\sim 0.40/\varepsilon$ at 95% confidence. This performance is a factor of $1.1\times$ and $14\times$ improvement over Rall and Fuller [Quantum 7, 937 (2023)], for worst-case complexity, which to our knowledge is the best published result for amplitude estimation. The approach presented here provides a simple, robust, parallel method to performing QAE, with many possible avenues for improvement borrowing ideas from the wealth of literature in classical signal processing. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.14697v1-abstract-full').style.display = 'none'; document.getElementById('2405.14697v1-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 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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, 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/2404.10088">arXiv:2404.10088</a> <span> [<a href="https://arxiv.org/pdf/2404.10088">pdf</a>, <a href="https://arxiv.org/format/2404.10088">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="Computational Finance">q-fin.CP</span> </div> </div> <p class="title is-5 mathjax"> Quantum Risk Analysis of Financial Derivatives </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Stamatopoulos%2C+N">Nikitas Stamatopoulos</a>, <a href="/search/quant-ph?searchtype=author&query=Clader%2C+B+D">B. David Clader</a>, <a href="/search/quant-ph?searchtype=author&query=Woerner%2C+S">Stefan Woerner</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2404.10088v1-abstract-short" style="display: inline;"> We introduce two quantum algorithms to compute the Value at Risk (VaR) and Conditional Value at Risk (CVaR) of financial derivatives using quantum computers: the first by applying existing ideas from quantum risk analysis to derivative pricing, and the second based on a novel approach using Quantum Signal Processing (QSP). Previous work in the literature has shown that quantum advantage is possibl… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.10088v1-abstract-full').style.display = 'inline'; document.getElementById('2404.10088v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.10088v1-abstract-full" style="display: none;"> We introduce two quantum algorithms to compute the Value at Risk (VaR) and Conditional Value at Risk (CVaR) of financial derivatives using quantum computers: the first by applying existing ideas from quantum risk analysis to derivative pricing, and the second based on a novel approach using Quantum Signal Processing (QSP). Previous work in the literature has shown that quantum advantage is possible in the context of individual derivative pricing and that advantage can be leveraged in a straightforward manner in the estimation of the VaR and CVaR. The algorithms we introduce in this work aim to provide an additional advantage by encoding the derivative price over multiple market scenarios in superposition and computing the desired values by applying appropriate transformations to the quantum system. We perform complexity and error analysis of both algorithms, and show that while the two algorithms have the same asymptotic scaling the QSP-based approach requires significantly fewer quantum resources for the same target accuracy. Additionally, by numerically simulating both quantum and classical VaR algorithms, we demonstrate that the quantum algorithm can extract additional advantage from a quantum computer compared to individual derivative pricing. Specifically, we show that under certain conditions VaR estimation can lower the latest published estimates of the logical clock rate required for quantum advantage in derivative pricing by up to $\sim 30$x. In light of these results, we are encouraged that our formulation of derivative pricing in the QSP framework may be further leveraged for quantum advantage in other relevant financial applications, and that quantum computers could be harnessed more efficiently by considering problems in the financial sector at a higher level. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.10088v1-abstract-full').style.display = 'none'; document.getElementById('2404.10088v1-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 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2404.07218">arXiv:2404.07218</a> <span> [<a href="https://arxiv.org/pdf/2404.07218">pdf</a>, <a href="https://arxiv.org/format/2404.07218">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Detectors">physics.ins-det</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Optics">physics.optics</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/10.1063/5.0193824">10.1063/5.0193824 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Miniaturized time-correlated single-photon counting module for time-of-flight non-line-of-sight imaging applications </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Wu%2C+J">Jie Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+C">Chao Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jian-Wei Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Dai%2C+C">Chen Dai</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+F">Feihu Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+J">Jun Zhang</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="2404.07218v1-abstract-short" style="display: inline;"> Single-photon time-of-flight (TOF) non-line-of-sight (NLOS) imaging enables the high-resolution reconstruction of objects outside the field of view. The compactness of TOF NLOS imaging systems, entailing the miniaturization of key components within such systems is crucial for practical applications. Here, we present a miniaturized four-channel time-correlated single-photon counting module dedicate… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.07218v1-abstract-full').style.display = 'inline'; document.getElementById('2404.07218v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.07218v1-abstract-full" style="display: none;"> Single-photon time-of-flight (TOF) non-line-of-sight (NLOS) imaging enables the high-resolution reconstruction of objects outside the field of view. The compactness of TOF NLOS imaging systems, entailing the miniaturization of key components within such systems is crucial for practical applications. Here, we present a miniaturized four-channel time-correlated single-photon counting module dedicated to TOF NLOS imaging applications. The module achieves excellent performance with a 10 ps bin size and 27.4 ps minimum root-mean-square time resolution. We present the results of TOF NLOS imaging experiment using an InGaAs/InP single-photon detector and the time-correlated single-photon counting module, and show that a 6.3 cm lateral resolution and 2.3 cm depth resolution can be achieved under the conditions of 5 m imaging distance and 1 ms pixel dwell time. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.07218v1-abstract-full').style.display = 'none'; document.getElementById('2404.07218v1-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> 9 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">Published by Review of Scientific Instrument</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Rev. Sci. Instrum. 95, 035107 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.08888">arXiv:2402.08888</a> <span> [<a href="https://arxiv.org/pdf/2402.08888">pdf</a>, <a href="https://arxiv.org/format/2402.08888">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"> Quantum Light Generation based on GaN Microring towards Fully On-chip Source </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+H">Hong Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=He%2C+Z">Zhao-Qin He</a>, <a href="/search/quant-ph?searchtype=author&query=Fan%2C+Y">Yun-Ru Fan</a>, <a href="/search/quant-ph?searchtype=author&query=Luo%2C+Y">Yue Luo</a>, <a href="/search/quant-ph?searchtype=author&query=Lyu%2C+C">Chen Lyu</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+J">Jin-Peng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+Y">Yun-Bo Li</a>, <a href="/search/quant-ph?searchtype=author&query=Liu%2C+S">Sheng Liu</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+D">Dong Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+D">De-Chao Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Juan-Juan Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+G">Guang-Wei Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+Y">You Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Song%2C+H">Hai-Zhi Song</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+Z">Zhen Wang</a>, <a href="/search/quant-ph?searchtype=author&query=You%2C+L">Li-Xing You</a>, <a href="/search/quant-ph?searchtype=author&query=Guo%2C+K">Kai Guo</a>, <a href="/search/quant-ph?searchtype=author&query=Sun%2C+C">Chang-Zheng Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Luo%2C+Y">Yi Luo</a>, <a href="/search/quant-ph?searchtype=author&query=Guo%2C+G">Guang-Can Guo</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+Q">Qiang Zhou</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="2402.08888v1-abstract-short" style="display: inline;"> Integrated quantum light source is increasingly desirable in large-scale quantum information processing.~Despite recent remarkable advances, new material platform is constantly being explored for the fully on-chip integration of quantum light generation, active and passive manipulation, and detection. Here, for the first time, we demonstrate a gallium nitride (GaN) microring based quantum light ge… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.08888v1-abstract-full').style.display = 'inline'; document.getElementById('2402.08888v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.08888v1-abstract-full" style="display: none;"> Integrated quantum light source is increasingly desirable in large-scale quantum information processing.~Despite recent remarkable advances, new material platform is constantly being explored for the fully on-chip integration of quantum light generation, active and passive manipulation, and detection. Here, for the first time, we demonstrate a gallium nitride (GaN) microring based quantum light generation in the telecom C-band, which has potential towards the monolithic integration of quantum light source.~In our demonstration, the GaN microring has a free spectral range of 330 GHz and a near-zero anomalous dispersion region of over 100 nm. The generation of energy-time entangled photon pair is demonstrated with a typical raw two-photon interference visibility of 95.5$\pm$6.5%, which is further configured to generate heralded single photon with a typical heralded second-order auto-correlation $g^{(2)}_{H}(0)$ of 0.045$\pm$0.001. Our results pave the way for developing chip-scale quantum photonic circuit. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.08888v1-abstract-full').style.display = 'none'; document.getElementById('2402.08888v1-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> 13 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.16317">arXiv:2401.16317</a> <span> [<a href="https://arxiv.org/pdf/2401.16317">pdf</a>, <a href="https://arxiv.org/format/2401.16317">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="Physics and Society">physics.soc-ph</span> </div> </div> <p class="title is-5 mathjax"> Assessing the Benefits and Risks of Quantum Computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Scholten%2C+T+L">Travis L. Scholten</a>, <a href="/search/quant-ph?searchtype=author&query=Williams%2C+C+J">Carl J. Williams</a>, <a href="/search/quant-ph?searchtype=author&query=Moody%2C+D">Dustin Moody</a>, <a href="/search/quant-ph?searchtype=author&query=Mosca%2C+M">Michele Mosca</a>, <a href="/search/quant-ph?searchtype=author&query=Hurley%2C+W">William Hurley</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Troyer%2C+M">Matthias Troyer</a>, <a href="/search/quant-ph?searchtype=author&query=Gambetta%2C+J+M">Jay M. Gambetta</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="2401.16317v2-abstract-short" style="display: inline;"> Quantum computing is an emerging technology with potentially far-reaching implications for national prosperity and security. Understanding the timeframes over which economic benefits and national security risks may manifest themselves is vital for ensuring the prudent development of this technology. To inform security experts and policy decision makers on this matter, we review what is currently k… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.16317v2-abstract-full').style.display = 'inline'; document.getElementById('2401.16317v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.16317v2-abstract-full" style="display: none;"> Quantum computing is an emerging technology with potentially far-reaching implications for national prosperity and security. Understanding the timeframes over which economic benefits and national security risks may manifest themselves is vital for ensuring the prudent development of this technology. To inform security experts and policy decision makers on this matter, we review what is currently known on the potential uses and risks of quantum computers, leveraging current research literature. The maturity of currently-available quantum computers is not yet at a level such that they can be used in production for large-scale, industrially-relevant problems, and they are not believed to currently pose security risks. We identify 2 large-scale trends -- new approximate methods (variational algorithms, error mitigation, and circuit knitting) and the commercial exploration of business-relevant quantum applications -- which, together, may enable useful and practical quantum computing in the near future. Crucially, these methods do not appear likely to change the required resources for cryptanalysis on currently-used cryptosystems. From an analysis we perform of the current and known algorithms for cryptanalysis, we find they require circuits of a size exceeding those that can be run by current and near-future quantum computers (and which will require error correction), though we acknowledge improvements in quantum algorithms for these problems are taking place in the literature. In addition, the risk to cybersecurity can be well-managed by the migration to new, quantum-safe cryptographic protocols, which we survey and discuss. Given the above, we conclude there is a credible expectation that quantum computers will be capable of performing computations which are economically-impactful before they will be capable of performing ones which are cryptographically-relevant. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.16317v2-abstract-full').style.display = 'none'; document.getElementById('2401.16317v2-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> 13 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">Relative to v1: fix typos throughout, correct and update Table III, add 8 references</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.03002">arXiv:2308.03002</a> <span> [<a href="https://arxiv.org/pdf/2308.03002">pdf</a>, <a href="https://arxiv.org/ps/2308.03002">ps</a>, <a href="https://arxiv.org/format/2308.03002">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 effect of Quantum Statistics on the sensitivity in an SU(1,1) interferometer </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jie Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Ding%2C+Y">Yingxing Ding</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+M">Mengyao Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Jiao%2C+G">Gao-Feng Jiao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+K">Keye Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+L+Q">L. Q. Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+W">Weiping Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Yuan%2C+C">Chun-Hua Yuan</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="2308.03002v1-abstract-short" style="display: inline;"> We theoretically study the effect of quantum statistics of the light field on the quantum enhancement of parameter estimation based on cat state input the SU(1,1) interferometer. The phase sensitivity is dependent on the relative phase $胃$ between two coherent states of Schr枚dinger cat states. The optimal sensitivity is achieved when the relative phase is $蟺$% , i.e., odd coherent states input. Fo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.03002v1-abstract-full').style.display = 'inline'; document.getElementById('2308.03002v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.03002v1-abstract-full" style="display: none;"> We theoretically study the effect of quantum statistics of the light field on the quantum enhancement of parameter estimation based on cat state input the SU(1,1) interferometer. The phase sensitivity is dependent on the relative phase $胃$ between two coherent states of Schr枚dinger cat states. The optimal sensitivity is achieved when the relative phase is $蟺$% , i.e., odd coherent states input. For a coherent state input into one port, the phase sensitivity of the odd coherent state into the second input port is inferior to that of the squeezed vacuum state input. However, in the presence of losses the Schr枚dinger cat states are more resistant to loss than squeezed vacuum states. As the amplitude of Schr枚dinger cat states increases, the quantum enhancement of phase sensitivity decreases, which shows that the quantum statistics of Schr枚dinger cat states tends towards Poisson statistics from sub-Poisson statistics or super-Poisson statistics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.03002v1-abstract-full').style.display = 'none'; document.getElementById('2308.03002v1-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 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">8 pages, 5 figures. arXiv admin note: text overlap with arXiv:2302.09823</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2307.14310">arXiv:2307.14310</a> <span> [<a href="https://arxiv.org/pdf/2307.14310">pdf</a>, <a href="https://arxiv.org/format/2307.14310">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="Computational Finance">q-fin.CP</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-2024-04-30-1322">10.22331/q-2024-04-30-1322 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Derivative Pricing using Quantum Signal Processing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Stamatopoulos%2C+N">Nikitas Stamatopoulos</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2307.14310v2-abstract-short" style="display: inline;"> Pricing financial derivatives on quantum computers typically includes quantum arithmetic components which contribute heavily to the quantum resources required by the corresponding circuits. In this manuscript, we introduce a method based on Quantum Signal Processing (QSP) to encode financial derivative payoffs directly into quantum amplitudes, alleviating the quantum circuits from the burden of co… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.14310v2-abstract-full').style.display = 'inline'; document.getElementById('2307.14310v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2307.14310v2-abstract-full" style="display: none;"> Pricing financial derivatives on quantum computers typically includes quantum arithmetic components which contribute heavily to the quantum resources required by the corresponding circuits. In this manuscript, we introduce a method based on Quantum Signal Processing (QSP) to encode financial derivative payoffs directly into quantum amplitudes, alleviating the quantum circuits from the burden of costly quantum arithmetic. Compared to current state-of-the-art approaches in the literature, we find that for derivative contracts of practical interest, the application of QSP significantly reduces the required resources across all metrics considered, most notably the total number of T-gates by $\sim 16$x and the number of logical qubits by $\sim 4$x. Additionally, we estimate that the logical clock rate needed for quantum advantage is also reduced by a factor of $\sim 5$x. Overall, we find that quantum advantage will require $4.7$k logical qubits, and quantum devices that can execute $10^9$ T-gates at a rate of $45$MHz. While in this work we focus specifically on the payoff component of the derivative pricing process where the method we present is most readily applicable, similar techniques can be employed to further reduce the resources in other applications, such as state preparation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.14310v2-abstract-full').style.display = 'none'; document.getElementById('2307.14310v2-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 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum 8, 1322 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.15863">arXiv:2306.15863</a> <span> [<a href="https://arxiv.org/pdf/2306.15863">pdf</a>, <a href="https://arxiv.org/format/2306.15863">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="Data Structures and Algorithms">cs.DS</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/10.1145/3680290">10.1145/3680290 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Increasing the Measured Effective Quantum Volume with Zero Noise Extrapolation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Pelofske%2C+E">Elijah Pelofske</a>, <a href="/search/quant-ph?searchtype=author&query=Russo%2C+V">Vincent Russo</a>, <a href="/search/quant-ph?searchtype=author&query=LaRose%2C+R">Ryan LaRose</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Strano%2C+D">Dan Strano</a>, <a href="/search/quant-ph?searchtype=author&query=B%C3%A4rtschi%2C+A">Andreas B盲rtschi</a>, <a href="/search/quant-ph?searchtype=author&query=Eidenbenz%2C+S">Stephan Eidenbenz</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2306.15863v2-abstract-short" style="display: inline;"> Quantum Volume is a full-stack benchmark for near-term quantum computers. It quantifies the largest size of a square circuit which can be executed on the target device with reasonable fidelity. Error mitigation is a set of techniques intended to remove the effects of noise present in the computation of noisy quantum computers when computing an expectation value of interest. Effective quantum volum… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.15863v2-abstract-full').style.display = 'inline'; document.getElementById('2306.15863v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.15863v2-abstract-full" style="display: none;"> Quantum Volume is a full-stack benchmark for near-term quantum computers. It quantifies the largest size of a square circuit which can be executed on the target device with reasonable fidelity. Error mitigation is a set of techniques intended to remove the effects of noise present in the computation of noisy quantum computers when computing an expectation value of interest. Effective quantum volume is a proposed metric that applies error mitigation to the quantum volume protocol in order to evaluate the effectiveness not only of the target device but also of the error mitigation algorithm. Digital Zero-Noise Extrapolation (ZNE) is an error mitigation technique that estimates the noiseless expectation value using circuit folding to amplify errors by known scale factors and extrapolating to the zero-noise limit. Here we demonstrate that ZNE, with global and local unitary folding with fractional scale factors, in conjunction with dynamical decoupling, can increase the effective quantum volume over the vendor-measured quantum volume. Specifically, we measure the effective quantum volume of four IBM Quantum superconducting processor units, obtaining values that are larger than the vendor-measured quantum volume on each device. This is the first such increase reported. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.15863v2-abstract-full').style.display = 'none'; document.getElementById('2306.15863v2-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 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 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">Report number:</span> LA-UR-23-26260 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ACM Transactions on Quantum Computing, 2024 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.06795">arXiv:2305.06795</a> <span> [<a href="https://arxiv.org/pdf/2305.06795">pdf</a>, <a href="https://arxiv.org/format/2305.06795">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"> Enhancing Quantum Circuit Noise Robustness from a Geometric Perspective </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Hai%2C+Y">Yong-Ju Hai</a>, <a href="/search/quant-ph?searchtype=author&query=Liang%2C+H">Hao Liang</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+X">Xiu-Hao 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="2305.06795v3-abstract-short" style="display: inline;"> Quantum errors in noisy environments remain a major obstacle to advancing quantum information technology. In this work, we expand a recently developed geometric framework, originally utilized for analyzing noise accumulation and creating dynamical error-correcting gates at the control pulse level, to now study noise dynamics at the quantum circuit level. Through a geometric perspective, we demonst… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.06795v3-abstract-full').style.display = 'inline'; document.getElementById('2305.06795v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.06795v3-abstract-full" style="display: none;"> Quantum errors in noisy environments remain a major obstacle to advancing quantum information technology. In this work, we expand a recently developed geometric framework, originally utilized for analyzing noise accumulation and creating dynamical error-correcting gates at the control pulse level, to now study noise dynamics at the quantum circuit level. Through a geometric perspective, we demonstrate how circuit noise robustness can be enhanced using twirling techniques. Additionally, we show that circuits modified by random twirling correspond to random walk trajectories in this geometric framework, and provide a fresh perspective on randomized compiling by analytically deriving the perturbative expression for the resultant Pauli noise channel. We also illustrate that combining robustness optimization strategies at both the control pulse and circuit levels can significantly boost overall circuit fidelity even further through numerical examples. This research illuminates pathways to achieving noise-resistant quantum control beyond mere optimization of control pulses. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.06795v3-abstract-full').style.display = 'none'; document.getElementById('2305.06795v3-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 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.14985">arXiv:2304.14985</a> <span> [<a href="https://arxiv.org/pdf/2304.14985">pdf</a>, <a href="https://arxiv.org/format/2304.14985">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/10.1109/QCE57702.2023.00103">10.1109/QCE57702.2023.00103 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Zero noise extrapolation on logical qubits by scaling the error correction code distance </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Wahl%2C+M+A">Misty A. Wahl</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Shammah%2C+N">Nathan Shammah</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Ravi%2C+G+S">Gokul Subramanian Ravi</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="2304.14985v2-abstract-short" style="display: inline;"> In this work, we migrate the quantum error mitigation technique of Zero-Noise Extrapolation (ZNE) to fault-tolerant quantum computing. We employ ZNE on logically encoded qubits rather than physical qubits. This approach will be useful in a regime where quantum error correction (QEC) is implementable but the number of qubits available for QEC is limited. Apart from illustrating the utility of a tra… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.14985v2-abstract-full').style.display = 'inline'; document.getElementById('2304.14985v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.14985v2-abstract-full" style="display: none;"> In this work, we migrate the quantum error mitigation technique of Zero-Noise Extrapolation (ZNE) to fault-tolerant quantum computing. We employ ZNE on logically encoded qubits rather than physical qubits. This approach will be useful in a regime where quantum error correction (QEC) is implementable but the number of qubits available for QEC is limited. Apart from illustrating the utility of a traditional ZNE approach (circuit-level unitary folding) for the QEC regime, we propose a novel noise scaling ZNE method specifically tailored to QEC: distance scaled ZNE (DS-ZNE). DS-ZNE scales the distance of the error correction code, and thereby the resulting logical error rate, and utilizes this code distance as the scaling `knob' for ZNE. Logical qubit error rates are scaled until the maximum achievable code distance for a fixed number of physical qubits, and lower error rates (i.e., effectively higher code distances) are achieved via extrapolation techniques migrated from traditional ZNE. Furthermore, to maximize physical qubit utilization over the ZNE experiments, logical executions at code distances lower than the maximum allowed by the physical qubits on the quantum device are parallelized to optimize device utilization. We validate our proposal with numerical simulation and confirm that ZNE lowers the logical error rates and increases the effective code distance beyond the physical capability of the quantum device. For instance, at a physical code distance of 11, the DS-ZNE effective code distance is 17, and at a physical code distance of 13, the DS-ZNE effective code distance is 21. When the proposed technique is compared against unitary folding ZNE under the constraint of a fixed number of executions of the quantum device, DS-ZNE outperforms unitary folding by up to 92% in terms of the post-ZNE logical error rate. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.14985v2-abstract-full').style.display = 'none'; document.getElementById('2304.14985v2-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 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">10 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2023 IEEE International Conference on Quantum Computing and Engineering (QCE) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.14969">arXiv:2304.14969</a> <span> [<a href="https://arxiv.org/pdf/2304.14969">pdf</a>, <a href="https://arxiv.org/format/2304.14969">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"> Exact and approximate simulation of large quantum circuits on a single GPU </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Strano%2C+D">Daniel Strano</a>, <a href="/search/quant-ph?searchtype=author&query=Bollay%2C+B">Benn Bollay</a>, <a href="/search/quant-ph?searchtype=author&query=Blaauw%2C+A">Aryan Blaauw</a>, <a href="/search/quant-ph?searchtype=author&query=Shammah%2C+N">Nathan Shammah</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</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="2304.14969v2-abstract-short" style="display: inline;"> We benchmark the performances of Qrack, an open-source software library for the high-performance classical simulation of (gate-model) quantum computers. Qrack simulates, in the Schr枚dinger picture, the exact quantum state of $n$ qubits evolving under the application of a circuit composed of elementary quantum gates. Moreover, Qrack can also run approximate simulations in which a tunable reduction… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.14969v2-abstract-full').style.display = 'inline'; document.getElementById('2304.14969v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.14969v2-abstract-full" style="display: none;"> We benchmark the performances of Qrack, an open-source software library for the high-performance classical simulation of (gate-model) quantum computers. Qrack simulates, in the Schr枚dinger picture, the exact quantum state of $n$ qubits evolving under the application of a circuit composed of elementary quantum gates. Moreover, Qrack can also run approximate simulations in which a tunable reduction of the quantum state fidelity is traded for a significant reduction of the execution time and memory footprint. In this work, we give an overview of both simulation methods (exact and approximate), highlighting the main physics-based and software-based techniques. Moreover, we run computationally heavy benchmarks on a single GPU, executing large quantum Fourier transform circuits and large random circuits. Compared with other classical simulators, we report competitive execution times for the exact simulation of Fourier transform circuits with up to 27 qubits. We also demonstrate the approximate simulation of all amplitudes of random circuits acting on 54 qubits with 7 layers at average fidelity higher than $4\%$, a task commonly considered hard without super-computing resources. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.14969v2-abstract-full').style.display = 'none'; document.getElementById('2304.14969v2-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">v1</span> submitted 28 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">(Accepted by IEEE Quantum Week 2023, Submission: 254)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2303.04061">arXiv:2303.04061</a> <span> [<a href="https://arxiv.org/pdf/2303.04061">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 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/10.1007/s11467-022-1249-z">10.1007/s11467-022-1249-z <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Noisy intermediate-scale quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cheng%2C+B">Bin Cheng</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+X">Xiu-Hao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Gu%2C+X">Xiu Gu</a>, <a href="/search/quant-ph?searchtype=author&query=He%2C+Y">Yu He</a>, <a href="/search/quant-ph?searchtype=author&query=Hu%2C+G">Guangchong Hu</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+P">Peihao Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+J">Jun Li</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+B">Ben-Chuan Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Lu%2C+D">Dawei Lu</a>, <a href="/search/quant-ph?searchtype=author&query=Lu%2C+Y">Yao Lu</a>, <a href="/search/quant-ph?searchtype=author&query=Qiu%2C+C">Chudan Qiu</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+H">Hui Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Xin%2C+T">Tao Xin</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+S">Shi Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Yung%2C+M">Man-Hong Yung</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+S">Song Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Zhong%2C+Y">Youpeng Zhong</a>, <a href="/search/quant-ph?searchtype=author&query=Peng%2C+X">Xinhua Peng</a>, <a href="/search/quant-ph?searchtype=author&query=Nori%2C+F">Franco Nori</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+D">Dapeng Yu</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="2303.04061v1-abstract-short" style="display: inline;"> Quantum computers have made extraordinary progress over the past decade, and significant milestones have been achieved along the path of pursuing universal fault-tolerant quantum computers. Quantum advantage, the tipping point heralding the quantum era, has been accomplished along with several waves of breakthroughs. Quantum hardware has become more integrated and architectural compared to its tod… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.04061v1-abstract-full').style.display = 'inline'; document.getElementById('2303.04061v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.04061v1-abstract-full" style="display: none;"> Quantum computers have made extraordinary progress over the past decade, and significant milestones have been achieved along the path of pursuing universal fault-tolerant quantum computers. Quantum advantage, the tipping point heralding the quantum era, has been accomplished along with several waves of breakthroughs. Quantum hardware has become more integrated and architectural compared to its toddler days. The controlling precision of various physical systems is pushed beyond the fault-tolerant threshold. Meanwhile, quantum computation research has established a new norm by embracing industrialization and commercialization. The joint power of governments, private investors, and tech companies has significantly shaped a new vibrant environment that accelerates the development of this field, now at the beginning of the noisy intermediate-scale quantum era. Here, we first discuss the progress achieved in the field of quantum computation by reviewing the most important algorithms and advances in the most promising technical routes, and then summarizing the next-stage challenges. Furthermore, we illustrate our confidence that solid foundations have been built for the fault-tolerant quantum computer and our optimism that the emergence of quantum killer applications essential for human society shall happen in the future. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.04061v1-abstract-full').style.display = 'none'; document.getElementById('2303.04061v1-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 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Front. Phys. 18, 21308 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.09823">arXiv:2302.09823</a> <span> [<a href="https://arxiv.org/pdf/2302.09823">pdf</a>, <a href="https://arxiv.org/ps/2302.09823">ps</a>, <a href="https://arxiv.org/format/2302.09823">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"> Ultimate precision limit of SU(2) and SU(1,1) interferometers in noisy metrology </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jie Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+D">Dong Li</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+L+Q">L. Q. Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+W">Weiping Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Yuan%2C+C">Chun-Hua Yuan</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="2302.09823v1-abstract-short" style="display: inline;"> The quantum Fisher information (QFI) in SU(2) and SU(1,1) interferometers was considered, and the QFI-only calculation was overestimated. In general, the phase estimation as a two-parameter estimation problem, and the quantum Fisher information matrix (QFIM) is necessary. In this paper, we theoretically generalize the model developed by Escher et al [Nature Physics 7, 406 (2011)] to the QFIM case… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.09823v1-abstract-full').style.display = 'inline'; document.getElementById('2302.09823v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.09823v1-abstract-full" style="display: none;"> The quantum Fisher information (QFI) in SU(2) and SU(1,1) interferometers was considered, and the QFI-only calculation was overestimated. In general, the phase estimation as a two-parameter estimation problem, and the quantum Fisher information matrix (QFIM) is necessary. In this paper, we theoretically generalize the model developed by Escher et al [Nature Physics 7, 406 (2011)] to the QFIM case with noise and study the ultimate precision limits of SU(2) and SU(1,1) interferometers with photon losses because photon losses as a very usual noise may happen to the phase measurement process. Using coherent state and squeezed vacuum state as a specific example, we numerically analyze the variation of the overestimated QFI with the loss coefficient, and find its disappearance and recovery phenomenon. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.09823v1-abstract-full').style.display = 'none'; document.getElementById('2302.09823v1-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, 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/2302.06212">arXiv:2302.06212</a> <span> [<a href="https://arxiv.org/pdf/2302.06212">pdf</a>, <a href="https://arxiv.org/format/2302.06212">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="Optics">physics.optics</span> </div> </div> <p class="title is-5 mathjax"> Quantum Key Distribution Using a Quantum Emitter in Hexagonal Boron Nitride </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Al-Juboori%2C+A">Ali Al-Juboori</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+H+Z+J">Helen Zhi Jie Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Nguyen%2C+M+A+P">Minh Anh Phan Nguyen</a>, <a href="/search/quant-ph?searchtype=author&query=Ai%2C+X">Xiaoyu Ai</a>, <a href="/search/quant-ph?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/quant-ph?searchtype=author&query=Solntsev%2C+A">Alexander Solntsev</a>, <a href="/search/quant-ph?searchtype=author&query=Toth%2C+M">Milos Toth</a>, <a href="/search/quant-ph?searchtype=author&query=Malaney%2C+R">Robert Malaney</a>, <a href="/search/quant-ph?searchtype=author&query=Aharonovich%2C+I">Igor Aharonovich</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="2302.06212v2-abstract-short" style="display: inline;"> Quantum Key Distribution (QKD) is considered the most immediate application to be widely implemented amongst a variety of potential quantum technologies. QKD enables sharing secret keys between distant users, using photons as information carriers. An ongoing endeavour is to implement these protocols in practice in a robust, and compact manner so as to be efficiently deployable in a range of real-w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.06212v2-abstract-full').style.display = 'inline'; document.getElementById('2302.06212v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.06212v2-abstract-full" style="display: none;"> Quantum Key Distribution (QKD) is considered the most immediate application to be widely implemented amongst a variety of potential quantum technologies. QKD enables sharing secret keys between distant users, using photons as information carriers. An ongoing endeavour is to implement these protocols in practice in a robust, and compact manner so as to be efficiently deployable in a range of real-world scenarios. Single Photon Sources (SPS) in solid-state materials are prime candidates in this respect. Here, we demonstrate a room temperature, discrete-variable quantum key distribution system using a bright single photon source in hexagonal-boron nitride, operating in free-space. Employing an easily interchangeable photon source system, we have generated keys with one million bits length, and demonstrated a secret key of approximately 70,000 bits, at a quantum bit error rate of 6%, with $\varepsilon$-security of $10^{-10}$. Our work demonstrates the first proof of concept finite-key BB84 QKD system realised with hBN defects. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.06212v2-abstract-full').style.display = 'none'; document.getElementById('2302.06212v2-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 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 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/2211.12489">arXiv:2211.12489</a> <span> [<a href="https://arxiv.org/pdf/2211.12489">pdf</a>, <a href="https://arxiv.org/format/2211.12489">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.4.040325">10.1103/PRXQuantum.4.040325 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> End-to-end resource analysis for quantum interior point methods and portfolio optimization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Dalzell%2C+A+M">Alexander M. Dalzell</a>, <a href="/search/quant-ph?searchtype=author&query=Clader%2C+B+D">B. David Clader</a>, <a href="/search/quant-ph?searchtype=author&query=Salton%2C+G">Grant Salton</a>, <a href="/search/quant-ph?searchtype=author&query=Berta%2C+M">Mario Berta</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+C+Y">Cedric Yen-Yu Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Bader%2C+D+A">David A. Bader</a>, <a href="/search/quant-ph?searchtype=author&query=Stamatopoulos%2C+N">Nikitas Stamatopoulos</a>, <a href="/search/quant-ph?searchtype=author&query=Schuetz%2C+M+J+A">Martin J. A. Schuetz</a>, <a href="/search/quant-ph?searchtype=author&query=Brand%C3%A3o%2C+F+G+S+L">Fernando G. S. L. Brand茫o</a>, <a href="/search/quant-ph?searchtype=author&query=Katzgraber%2C+H+G">Helmut G. Katzgraber</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2211.12489v2-abstract-short" style="display: inline;"> We study quantum interior point methods (QIPMs) for second-order cone programming (SOCP), guided by the example use case of portfolio optimization (PO). We provide a complete quantum circuit-level description of the algorithm from problem input to problem output, making several improvements to the implementation of the QIPM. We report the number of logical qubits and the quantity/depth of non-Clif… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.12489v2-abstract-full').style.display = 'inline'; document.getElementById('2211.12489v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.12489v2-abstract-full" style="display: none;"> We study quantum interior point methods (QIPMs) for second-order cone programming (SOCP), guided by the example use case of portfolio optimization (PO). We provide a complete quantum circuit-level description of the algorithm from problem input to problem output, making several improvements to the implementation of the QIPM. We report the number of logical qubits and the quantity/depth of non-Clifford T-gates needed to run the algorithm, including constant factors. The resource counts we find depend on instance-specific parameters, such as the condition number of certain linear systems within the problem. To determine the size of these parameters, we perform numerical simulations of small PO instances, which lead to concrete resource estimates for the PO use case. Our numerical results do not probe large enough instance sizes to make conclusive statements about the asymptotic scaling of the algorithm. However, already at small instance sizes, our analysis suggests that, due primarily to large constant pre-factors, poorly conditioned linear systems, and a fundamental reliance on costly quantum state tomography, fundamental improvements to the QIPM are required for it to lead to practical quantum advantage. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.12489v2-abstract-full').style.display = 'none'; document.getElementById('2211.12489v2-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 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">40 pages, 15 figures. v2: minor corrections and updates to match journal version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> PRX Quantum 4, 040325 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.06382">arXiv:2211.06382</a> <span> [<a href="https://arxiv.org/pdf/2211.06382">pdf</a>, <a href="https://arxiv.org/format/2211.06382">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"> Hardware optimized parity check gates for superconducting surface codes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Reagor%2C+M+J">Matthew J. Reagor</a>, <a href="/search/quant-ph?searchtype=author&query=Bohdanowicz%2C+T+C">Thomas C. Bohdanowicz</a>, <a href="/search/quant-ph?searchtype=author&query=Perez%2C+D+R">David Rodriguez Perez</a>, <a href="/search/quant-ph?searchtype=author&query=Sete%2C+E+A">Eyob A. Sete</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2211.06382v1-abstract-short" style="display: inline;"> Error correcting codes use multi-qubit measurements to realize fault-tolerant quantum logic steps. In fact, the resources needed to scale-up fault-tolerant quantum computing hardware are largely set by this task. Tailoring next-generation processors for joint measurements, therefore, could result in improvements to speed, accuracy, or cost -- accelerating the development large-scale quantum comput… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.06382v1-abstract-full').style.display = 'inline'; document.getElementById('2211.06382v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.06382v1-abstract-full" style="display: none;"> Error correcting codes use multi-qubit measurements to realize fault-tolerant quantum logic steps. In fact, the resources needed to scale-up fault-tolerant quantum computing hardware are largely set by this task. Tailoring next-generation processors for joint measurements, therefore, could result in improvements to speed, accuracy, or cost -- accelerating the development large-scale quantum computers. Here, we motivate such explorations by analyzing an unconventional surface code based on multi-body interactions between superconducting transmon qubits. Our central consideration, Hardware Optimized Parity (HOP) gates, achieves stabilizer-type measurements through simultaneous multi-qubit conditional phase accumulation. Despite the multi-body effects that underpin this approach, our estimates of logical faults suggest that this design can be at least as robust to realistic noise as conventional designs. We show a higher threshold of $1.25 \times 10^{-3}$ compared to the standard code's $0.79 \times 10^{-3}$. However, in the HOP code the logical error rate decreases more slowly with decreasing physical error rate. Our results point to a fruitful path forward towards extending gate-model platforms for error correction at the dawn of its empirical development. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.06382v1-abstract-full').style.display = 'none'; document.getElementById('2211.06382v1-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 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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 page manuscript (21 total), 10 manuscript figures (12 total)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.14521">arXiv:2210.14521</a> <span> [<a href="https://arxiv.org/pdf/2210.14521">pdf</a>, <a href="https://arxiv.org/format/2210.14521">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"> Universal robust quantum gates by geometric correspondence of noisy quantum dynamics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Hai%2C+Y">Yong-Ju Hai</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+J">Junning Li</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+X">Xiu-Hao 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="2210.14521v4-abstract-short" style="display: inline;"> Exposure to noises is a major obstacle for processing quantum information, but noises don't necessarily induce errors. Errors on the quantum gates could be suppressed via robust quantum control techniques. But understanding the genesis of errors and finding a universal treatment remains grueling. To resolve this issue, we develop a geometric theory to capture quantum dynamics due to various noises… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.14521v4-abstract-full').style.display = 'inline'; document.getElementById('2210.14521v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.14521v4-abstract-full" style="display: none;"> Exposure to noises is a major obstacle for processing quantum information, but noises don't necessarily induce errors. Errors on the quantum gates could be suppressed via robust quantum control techniques. But understanding the genesis of errors and finding a universal treatment remains grueling. To resolve this issue, we develop a geometric theory to capture quantum dynamics due to various noises graphically, obtaining the quantum erroneous evolution diagrams (QEED). Our theory provides explicit necessary and sufficient criteria for robust control Hamiltonian and quantitative geometric metrics of the gate error. We then develop a protocol to engineer a universal set of single- and two-qubit robust gates that correct the generic errors. Our numerical simulation shows gate fidelities above $99.99\%$ over a broad region of noise strength using simplest and smooth pulses for arbitrary gate time. Our approach offers new insights into the geometric aspects of noisy quantum dynamics and several advantages over existing methods, including the treatment of arbitrary noises, independence of system parameters, scalability, and being friendly to experiments. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.14521v4-abstract-full').style.display = 'none'; document.getElementById('2210.14521v4-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> 4 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">16 pages, 11 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/2210.11786">arXiv:2210.11786</a> <span> [<a href="https://arxiv.org/pdf/2210.11786">pdf</a>, <a href="https://arxiv.org/format/2210.11786">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="Emerging Technologies">cs.ET</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Programming Languages">cs.PL</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/10.1109/QCS56647.2022.00014">10.1109/QCS56647.2022.00014 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Q# Implementation of a Quantum Lookup Table for Quantum Arithmetic Functions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Krishnakumar%2C+R">Rajiv Krishnakumar</a>, <a href="/search/quant-ph?searchtype=author&query=Soeken%2C+M">Mathias Soeken</a>, <a href="/search/quant-ph?searchtype=author&query=Roetteler%2C+M">Martin Roetteler</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2210.11786v1-abstract-short" style="display: inline;"> In this paper, we present Q# implementations for arbitrary single-variabled fixed-point arithmetic operations for a gate-based quantum computer based on lookup tables (LUTs). In general, this is an inefficent way of implementing a function since the number of inputs can be large or even infinite. However, if the input domain can be bounded and there can be some error tolerance in the output (both… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.11786v1-abstract-full').style.display = 'inline'; document.getElementById('2210.11786v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.11786v1-abstract-full" style="display: none;"> In this paper, we present Q# implementations for arbitrary single-variabled fixed-point arithmetic operations for a gate-based quantum computer based on lookup tables (LUTs). In general, this is an inefficent way of implementing a function since the number of inputs can be large or even infinite. However, if the input domain can be bounded and there can be some error tolerance in the output (both of which are often the case in practical use-cases), the quantum LUT implementation of certain quantum arithmetic functions can be more efficient than their corresponding reversible arithmetic implementations. We discuss the implementation of the LUT using Q\# and its approximation errors. We then show examples of how to use the LUT to implement quantum arithmetic functions and compare the resources required for the implementation with the current state-of-the-art bespoke implementations of some commonly used arithmetic functions. The implementation of the LUT is designed for use by practitioners to use when implementing end-to-end quantum algorithms. In addition, given its well-defined approximation errors, the LUT implementation makes for a clear benchmark for evaluating the efficiency of bespoke quantum arithmetic circuits . <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.11786v1-abstract-full').style.display = 'none'; document.getElementById('2210.11786v1-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> 21 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2022 IEEE/ACM Third International Workshop on Quantum Computing Software (QCS), pp. 75-82 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.08611">arXiv:2210.08611</a> <span> [<a href="https://arxiv.org/pdf/2210.08611">pdf</a>, <a href="https://arxiv.org/format/2210.08611">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="Emerging Technologies">cs.ET</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/10.1109/QCS56647.2022.00015">10.1109/QCS56647.2022.00015 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Automated quantum error mitigation based on probabilistic error reduction </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=McDonough%2C+B">Benjamin McDonough</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Shammah%2C+N">Nathan Shammah</a>, <a href="/search/quant-ph?searchtype=author&query=Stemen%2C+N+T">Nathaniel T. Stemen</a>, <a href="/search/quant-ph?searchtype=author&query=Wahl%2C+M">Misty Wahl</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Orth%2C+P+P">Peter P. Orth</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="2210.08611v1-abstract-short" style="display: inline;"> Current quantum computers suffer from a level of noise that prohibits extracting useful results directly from longer computations. The figure of merit in many near-term quantum algorithms is an expectation value measured at the end of the computation, which experiences a bias in the presence of hardware noise. A systematic way to remove such bias is probabilistic error cancellation (PEC). PEC requ… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.08611v1-abstract-full').style.display = 'inline'; document.getElementById('2210.08611v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.08611v1-abstract-full" style="display: none;"> Current quantum computers suffer from a level of noise that prohibits extracting useful results directly from longer computations. The figure of merit in many near-term quantum algorithms is an expectation value measured at the end of the computation, which experiences a bias in the presence of hardware noise. A systematic way to remove such bias is probabilistic error cancellation (PEC). PEC requires a full characterization of the noise and introduces a sampling overhead that increases exponentially with circuit depth, prohibiting high-depth circuits at realistic noise levels. Probabilistic error reduction (PER) is a related quantum error mitigation method that systematically reduces the sampling overhead at the cost of reintroducing bias. In combination with zero-noise extrapolation, PER can yield expectation values with an accuracy comparable to PEC.Noise reduction through PER is broadly applicable to near-term algorithms, and the automated implementation of PER is thus desirable for facilitating its widespread use. To this end, we present an automated quantum error mitigation software framework that includes noise tomography and application of PER to user-specified circuits. We provide a multi-platform Python package that implements a recently developed Pauli noise tomography (PNT) technique for learning a sparse Pauli noise model and exploits a Pauli noise scaling method to carry out PER.We also provide software tools that leverage a previously developed toolchain, employing PyGSTi for gate set tomography and providing a functionality to use the software Mitiq for PER and zero-noise extrapolation to obtain error-mitigated expectation values on a user-defined circuit. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.08611v1-abstract-full').style.display = 'none'; document.getElementById('2210.08611v1-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 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">11 pages, 9 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2022 IEEE/ACM Third Int. Workshop Quantum Computing Software (QCS) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.07194">arXiv:2210.07194</a> <span> [<a href="https://arxiv.org/pdf/2210.07194">pdf</a>, <a href="https://arxiv.org/format/2210.07194">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="Emerging Technologies">cs.ET</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/10.1109/TQE.2023.3305232">10.1109/TQE.2023.3305232 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Testing platform-independent quantum error mitigation on noisy quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Russo%2C+V">Vincent Russo</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Shammah%2C+N">Nathan Shammah</a>, <a href="/search/quant-ph?searchtype=author&query=LaRose%2C+R">Ryan LaRose</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2210.07194v2-abstract-short" style="display: inline;"> We apply quantum error mitigation techniques to a variety of benchmark problems and quantum computers to evaluate the performance of quantum error mitigation in practice. To do so, we define an empirically motivated, resource-normalized metric of the improvement of error mitigation which we call the improvement factor, and calculate this metric for each experiment we perform. The experiments we pe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.07194v2-abstract-full').style.display = 'inline'; document.getElementById('2210.07194v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.07194v2-abstract-full" style="display: none;"> We apply quantum error mitigation techniques to a variety of benchmark problems and quantum computers to evaluate the performance of quantum error mitigation in practice. To do so, we define an empirically motivated, resource-normalized metric of the improvement of error mitigation which we call the improvement factor, and calculate this metric for each experiment we perform. The experiments we perform consist of zero-noise extrapolation and probabilistic error cancellation applied to two benchmark problems run on IBM, IonQ, and Rigetti quantum computers, as well as noisy quantum computer simulators. Our results show that error mitigation is on average more beneficial than no error mitigation - even when normalized by the additional resources used - but also emphasize that the performance of quantum error mitigation depends on the underlying computer. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.07194v2-abstract-full').style.display = 'none'; document.getElementById('2210.07194v2-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> 19 December, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2023 IEEE Transactions on Quantum Engineering </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2207.11645">arXiv:2207.11645</a> <span> [<a href="https://arxiv.org/pdf/2207.11645">pdf</a>, <a href="https://arxiv.org/format/2207.11645">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"> Maximum entropy methods for quantum state compatibility problems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Hou%2C+S">Shi-Yao Hou</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+Z">Zipeng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jinfeng Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+N">Ningping Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+Y">Youning Li</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+B">Bei Zeng</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="2207.11645v1-abstract-short" style="display: inline;"> Inferring a quantum system from incomplete information is a common problem in many aspects of quantum information science and applications, where the principle of maximum entropy (MaxEnt) plays an important role. The quantum state compatibility problem asks whether there exists a density matrix $蟻$ compatible with some given measurement results. Such a compatibility problem can be naturally formul… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.11645v1-abstract-full').style.display = 'inline'; document.getElementById('2207.11645v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2207.11645v1-abstract-full" style="display: none;"> Inferring a quantum system from incomplete information is a common problem in many aspects of quantum information science and applications, where the principle of maximum entropy (MaxEnt) plays an important role. The quantum state compatibility problem asks whether there exists a density matrix $蟻$ compatible with some given measurement results. Such a compatibility problem can be naturally formulated as a semidefinite programming (SDP), which searches directly for the existence of a $蟻$. However, for large system dimensions, it is hard to represent $蟻$ directly, since it needs too many parameters. In this work, we apply MaxEnt to solve various quantum state compatibility problems, including the quantum marginal problem. An immediate advantage of the MaxEnt method is that it only needs to represent $蟻$ via a relatively small number of parameters, which is exactly the number of the operators measured. Furthermore, in case of incompatible measurement results, our method will further return a witness that is a supporting hyperplane of the compatible set. Our method has a clear geometric meaning and can be computed effectively with hybrid quantum-classical algorithms. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.11645v1-abstract-full').style.display = 'none'; document.getElementById('2207.11645v1-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 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">11 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/2206.03505">arXiv:2206.03505</a> <span> [<a href="https://arxiv.org/pdf/2206.03505">pdf</a>, <a href="https://arxiv.org/format/2206.03505">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/10.1109/TQE.2022.3231194">10.1109/TQE.2022.3231194 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum Resources Required to Block-Encode a Matrix of Classical Data </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Clader%2C+B+D">B. David Clader</a>, <a href="/search/quant-ph?searchtype=author&query=Dalzell%2C+A+M">Alexander M. Dalzell</a>, <a href="/search/quant-ph?searchtype=author&query=Stamatopoulos%2C+N">Nikitas Stamatopoulos</a>, <a href="/search/quant-ph?searchtype=author&query=Salton%2C+G">Grant Salton</a>, <a href="/search/quant-ph?searchtype=author&query=Berta%2C+M">Mario Berta</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2206.03505v1-abstract-short" style="display: inline;"> We provide modular circuit-level implementations and resource estimates for several methods of block-encoding a dense $N\times N$ matrix of classical data to precision $蔚$; the minimal-depth method achieves a $T$-depth of $\mathcal{O}{(\log (N/蔚))},$ while the minimal-count method achieves a $T$-count of $\mathcal{O}{(N\log(1/蔚))}$. We examine resource tradeoffs between the different approaches, a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.03505v1-abstract-full').style.display = 'inline'; document.getElementById('2206.03505v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2206.03505v1-abstract-full" style="display: none;"> We provide modular circuit-level implementations and resource estimates for several methods of block-encoding a dense $N\times N$ matrix of classical data to precision $蔚$; the minimal-depth method achieves a $T$-depth of $\mathcal{O}{(\log (N/蔚))},$ while the minimal-count method achieves a $T$-count of $\mathcal{O}{(N\log(1/蔚))}$. We examine resource tradeoffs between the different approaches, and we explore implementations of two separate models of quantum random access memory (QRAM). As part of this analysis, we provide a novel state preparation routine with $T$-depth $\mathcal{O}{(\log (N/蔚))}$, improving on previous constructions with scaling $\mathcal{O}{(\log^2 (N/蔚))}$. Our results go beyond simple query complexity and provide a clear picture into the resource costs when large amounts of classical data are assumed to be accessible to quantum algorithms. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.03505v1-abstract-full').style.display = 'none'; document.getElementById('2206.03505v1-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 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">Journal ref:</span> IEEE Transactions on Quantum Engineering, vol. 3, pp. 1-23, 2022, Art no. 3103323 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2203.05489">arXiv:2203.05489</a> <span> [<a href="https://arxiv.org/pdf/2203.05489">pdf</a>, <a href="https://arxiv.org/format/2203.05489">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"> Error mitigation increases the effective quantum volume of quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=LaRose%2C+R">Ryan LaRose</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Russo%2C+V">Vincent Russo</a>, <a href="/search/quant-ph?searchtype=author&query=Strano%2C+D">Dan Strano</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2203.05489v2-abstract-short" style="display: inline;"> Quantum volume is a single-number metric which, loosely speaking, reports the number of usable qubits on a quantum computer. While improvements to the underlying hardware are a direct means of increasing quantum volume, the metric is "full-stack" and has also been increased by improvements to software, notably compilers. We extend this latter direction by demonstrating that error mitigation, a typ… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.05489v2-abstract-full').style.display = 'inline'; document.getElementById('2203.05489v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.05489v2-abstract-full" style="display: none;"> Quantum volume is a single-number metric which, loosely speaking, reports the number of usable qubits on a quantum computer. While improvements to the underlying hardware are a direct means of increasing quantum volume, the metric is "full-stack" and has also been increased by improvements to software, notably compilers. We extend this latter direction by demonstrating that error mitigation, a type of indirect compilation, increases the effective quantum volume of several quantum computers. Importantly, this increase occurs while taking the same number of overall samples. We encourage the adoption of quantum volume as a benchmark for assessing the performance of error mitigation techniques. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.05489v2-abstract-full').style.display = 'none'; document.getElementById('2203.05489v2-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 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">v2: Fix Fig. 1 subplot</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.11882">arXiv:2201.11882</a> <span> [<a href="https://arxiv.org/pdf/2201.11882">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="Optics">physics.optics</span> </div> </div> <p class="title is-5 mathjax"> Integrated Room Temperature Single Photon Source for Quantum Key Distribution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+H+Z+J">Helen Zhi Jie Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Ngyuen%2C+M+A+P">Minh Anh Phan Ngyuen</a>, <a href="/search/quant-ph?searchtype=author&query=Ai%2C+X">Xiaoyu Ai</a>, <a href="/search/quant-ph?searchtype=author&query=Bennet%2C+A">Adam Bennet</a>, <a href="/search/quant-ph?searchtype=author&query=Solnstev%2C+A">Alexander Solnstev</a>, <a href="/search/quant-ph?searchtype=author&query=Laucht%2C+A">Arne Laucht</a>, <a href="/search/quant-ph?searchtype=author&query=Al-Juboori%2C+A">Ali Al-Juboori</a>, <a href="/search/quant-ph?searchtype=author&query=Toth%2C+M">Milos Toth</a>, <a href="/search/quant-ph?searchtype=author&query=Mildren%2C+R">Rich Mildren</a>, <a href="/search/quant-ph?searchtype=author&query=Malaney%2C+R">Robert Malaney</a>, <a href="/search/quant-ph?searchtype=author&query=Aharonovich%2C+I">Igor Aharonovich</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="2201.11882v1-abstract-short" style="display: inline;"> High-purity single photon sources (SPS) that can operate at room temperature are highly desirable for a myriad of applications, including quantum photonics and quantum key distribution. In this work, we realise an ultra-bright solid-state SPS based on an atomic defect in hexagonal boron nitride (hBN) integrated with a solid immersion lens (SIL). The SIL increases the source efficiency by a factor… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.11882v1-abstract-full').style.display = 'inline'; document.getElementById('2201.11882v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.11882v1-abstract-full" style="display: none;"> High-purity single photon sources (SPS) that can operate at room temperature are highly desirable for a myriad of applications, including quantum photonics and quantum key distribution. In this work, we realise an ultra-bright solid-state SPS based on an atomic defect in hexagonal boron nitride (hBN) integrated with a solid immersion lens (SIL). The SIL increases the source efficiency by a factor of six, and the integrated system is capable of producing over ten million single photons per second at room temperature. Our results are promising for practical applications of SPS in quantum communication protocols. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.11882v1-abstract-full').style.display = 'none'; document.getElementById('2201.11882v1-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 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.11792">arXiv:2201.11792</a> <span> [<a href="https://arxiv.org/pdf/2201.11792">pdf</a>, <a href="https://arxiv.org/format/2201.11792">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.106.052406">10.1103/PhysRevA.106.052406 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Analyzing the impact of time-correlated noise on zero-noise extrapolation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Schultz%2C+K">Kevin Schultz</a>, <a href="/search/quant-ph?searchtype=author&query=LaRose%2C+R">Ryan LaRose</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Quiroz%2C+G">Gregory Quiroz</a>, <a href="/search/quant-ph?searchtype=author&query=Shammah%2C+N">Nathan Shammah</a>, <a href="/search/quant-ph?searchtype=author&query=Clader%2C+B+D">B. David Clader</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2201.11792v3-abstract-short" style="display: inline;"> Zero-noise extrapolation is a quantum error mitigation technique that has typically been studied under the ideal approximation that the noise acting on a quantum device is not time-correlated. In this work, we investigate the feasibility and performance of zero-noise extrapolation in the presence of time-correlated noise. We show that, in contrast to white noise, time-correlated noise is harder to… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.11792v3-abstract-full').style.display = 'inline'; document.getElementById('2201.11792v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.11792v3-abstract-full" style="display: none;"> Zero-noise extrapolation is a quantum error mitigation technique that has typically been studied under the ideal approximation that the noise acting on a quantum device is not time-correlated. In this work, we investigate the feasibility and performance of zero-noise extrapolation in the presence of time-correlated noise. We show that, in contrast to white noise, time-correlated noise is harder to mitigate via zero-noise extrapolation because it is difficult to scale the noise level without also modifying its spectral distribution. This limitation is particularly strong if "local" gate-level methods are applied for noise scaling. However, we find that "global" noise scaling methods, e.g., global unitary folding, can be sufficiently reliable even in the presence of time-correlated noise. We also introduce gate Trotterization as a new noise scaling technique that may be of independent interest. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.11792v3-abstract-full').style.display = 'none'; document.getElementById('2201.11792v3-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> 9 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 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">16 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. A 106, 052406 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.12509">arXiv:2111.12509</a> <span> [<a href="https://arxiv.org/pdf/2111.12509">pdf</a>, <a href="https://arxiv.org/format/2111.12509">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="Computational Finance">q-fin.CP</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-2022-07-20-770">10.22331/q-2022-07-20-770 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Towards Quantum Advantage in Financial Market Risk using Quantum Gradient Algorithms </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Stamatopoulos%2C+N">Nikitas Stamatopoulos</a>, <a href="/search/quant-ph?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/quant-ph?searchtype=author&query=Woerner%2C+S">Stefan Woerner</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2111.12509v2-abstract-short" style="display: inline;"> We introduce a quantum algorithm to compute the market risk of financial derivatives. Previous work has shown that quantum amplitude estimation can accelerate derivative pricing quadratically in the target error and we extend this to a quadratic error scaling advantage in market risk computation. We show that employing quantum gradient estimation algorithms can deliver a further quadratic advantag… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.12509v2-abstract-full').style.display = 'inline'; document.getElementById('2111.12509v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.12509v2-abstract-full" style="display: none;"> We introduce a quantum algorithm to compute the market risk of financial derivatives. Previous work has shown that quantum amplitude estimation can accelerate derivative pricing quadratically in the target error and we extend this to a quadratic error scaling advantage in market risk computation. We show that employing quantum gradient estimation algorithms can deliver a further quadratic advantage in the number of the associated market sensitivities, usually called greeks. By numerically simulating the quantum gradient estimation algorithms on financial derivatives of practical interest, we demonstrate that not only can we successfully estimate the greeks in the examples studied, but that the resource requirements can be significantly lower in practice than what is expected by theoretical complexity bounds. This additional advantage in the computation of financial market risk lowers the estimated logical clock rate required for financial quantum advantage from Chakrabarti et al. [Quantum 5, 463 (2021)] by a factor of ~7, from 50MHz to 7MHz, even for a modest number of greeks by industry standards (four). Moreover, we show that if we have access to enough resources, the quantum algorithm can be parallelized across 60 QPUs, in which case the logical clock rate of each device required to achieve the same overall runtime as the serial execution would be ~100kHz. Throughout this work, we summarize and compare several different combinations of quantum and classical approaches that could be used for computing the market risk of financial derivatives. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.12509v2-abstract-full').style.display = 'none'; document.getElementById('2111.12509v2-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> 18 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 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> Quantum 6, 770 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.02237">arXiv:2108.02237</a> <span> [<a href="https://arxiv.org/pdf/2108.02237">pdf</a>, <a href="https://arxiv.org/format/2108.02237">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.104.052607">10.1103/PhysRevA.104.052607 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Extending quantum probabilistic error cancellation by noise scaling </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Shammah%2C+N">Nathan Shammah</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2108.02237v2-abstract-short" style="display: inline;"> We propose a general framework for quantum error mitigation that combines and generalizes two techniques: probabilistic error cancellation (PEC) and zero-noise extrapolation (ZNE). Similarly to PEC, the proposed method represents ideal operations as linear combinations of noisy operations that are implementable on hardware. However, instead of assuming a fixed level of hardware noise, we extend th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.02237v2-abstract-full').style.display = 'inline'; document.getElementById('2108.02237v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.02237v2-abstract-full" style="display: none;"> We propose a general framework for quantum error mitigation that combines and generalizes two techniques: probabilistic error cancellation (PEC) and zero-noise extrapolation (ZNE). Similarly to PEC, the proposed method represents ideal operations as linear combinations of noisy operations that are implementable on hardware. However, instead of assuming a fixed level of hardware noise, we extend the set of implementable operations by noise scaling. By construction, this method encompasses both PEC and ZNE as particular cases and allows us to investigate a larger set of hybrid techniques. For example, gate extrapolation can be used to implement PEC without requiring knowledge of the device's noise model, e.g., avoiding gate set tomography. Alternatively, probabilistic error reduction can be used to estimate expectation values at intermediate virtual noise strengths (below the hardware level), obtaining partially mitigated results at a lower sampling cost. Moreover, multiple results obtained with different noise reduction factors can be further post-processed with ZNE to better approximate the zero-noise limit. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.02237v2-abstract-full').style.display = 'none'; document.getElementById('2108.02237v2-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 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 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">Comments:</span> <span class="has-text-grey-dark mathjax">Code repository: https://github.com/unitaryfund/research/tree/main/nepec</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 104, 052607 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.16015">arXiv:2103.16015</a> <span> [<a href="https://arxiv.org/pdf/2103.16015">pdf</a>, <a href="https://arxiv.org/format/2103.16015">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"> Dynamically corrected gates from geometric space curves </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Barnes%2C+E">Edwin Barnes</a>, <a href="/search/quant-ph?searchtype=author&query=Calderon-Vargas%2C+F+A">Fernando A. Calderon-Vargas</a>, <a href="/search/quant-ph?searchtype=author&query=Dong%2C+W">Wenzheng Dong</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+B">Bikun Li</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Zhuang%2C+F">Fei Zhuang</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="2103.16015v1-abstract-short" style="display: inline;"> Quantum information technologies demand highly accurate control over quantum systems. Achieving this requires control techniques that perform well despite the presence of decohering noise and other adverse effects. Here, we review a general technique for designing control fields that dynamically correct errors while performing operations using a close relationship between quantum evolution and geo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.16015v1-abstract-full').style.display = 'inline'; document.getElementById('2103.16015v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.16015v1-abstract-full" style="display: none;"> Quantum information technologies demand highly accurate control over quantum systems. Achieving this requires control techniques that perform well despite the presence of decohering noise and other adverse effects. Here, we review a general technique for designing control fields that dynamically correct errors while performing operations using a close relationship between quantum evolution and geometric space curves. This approach provides access to the global solution space of control fields that accomplish a given task, facilitating the design of experimentally feasible gate operations for a wide variety of applications. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.16015v1-abstract-full').style.display = 'none'; document.getElementById('2103.16015v1-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 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">Comments:</span> <span class="has-text-grey-dark mathjax">25 pages, 17 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/2103.08506">arXiv:2103.08506</a> <span> [<a href="https://arxiv.org/pdf/2103.08506">pdf</a>, <a href="https://arxiv.org/format/2103.08506">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/10.1088/1367-2630/ac22ea">10.1088/1367-2630/ac22ea <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Designing arbitrary single-axis rotations robust against perpendicular time-dependent noise </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Li%2C+B">Bikun Li</a>, <a href="/search/quant-ph?searchtype=author&query=Calderon-Vargas%2C+F+A">F. A. Calderon-Vargas</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Barnes%2C+E">Edwin Barnes</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="2103.08506v1-abstract-short" style="display: inline;"> Low-frequency time-dependent noise is one of the main obstacles on the road towards a fully scalable quantum computer. The majority of solid-state qubit platforms, from superconducting circuits to spins in semiconductors, are greatly affected by $1/f$ noise. Among the different control techniques used to counteract noise effects on the system, dynamical decoupling sequences are one of the most eff… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.08506v1-abstract-full').style.display = 'inline'; document.getElementById('2103.08506v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.08506v1-abstract-full" style="display: none;"> Low-frequency time-dependent noise is one of the main obstacles on the road towards a fully scalable quantum computer. The majority of solid-state qubit platforms, from superconducting circuits to spins in semiconductors, are greatly affected by $1/f$ noise. Among the different control techniques used to counteract noise effects on the system, dynamical decoupling sequences are one of the most effective. However, most dynamical decoupling sequences require unbounded and instantaneous pulses, which are unphysical and can only implement identity operations. Among methods that do restrict to bounded control fields, there remains a need for protocols that implement arbitrary gates with lab-ready control fields. In this work, we introduce a protocol to design bounded and continuous control fields that implement arbitrary single-axis rotations while shielding the system from low-frequency time-dependent noise perpendicular to the control axis. We show the versatility of our method by presenting a set of non-negative-only control pulses that are immediately applicable to quantum systems with constrained control, such as singlet-triplet spin qubits. Finally, we demonstrate the robustness of our control pulses against classical $1/f$ noise and noise modeled with a random quantum bath, showing that our pulses can even outperform ideal dynamical decoupling sequences. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.08506v1-abstract-full').style.display = 'none'; document.getElementById('2103.08506v1-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, 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">Comments:</span> <span class="has-text-grey-dark mathjax">11 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/2103.07586">arXiv:2103.07586</a> <span> [<a href="https://arxiv.org/pdf/2103.07586">pdf</a>, <a href="https://arxiv.org/format/2103.07586">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-2022-02-02-639">10.22331/q-2022-02-02-639 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Noise-resistant Landau-Zener sweeps from geometrical curves </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zhuang%2C+F">Fei Zhuang</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</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=Barnes%2C+E">Edwin Barnes</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="2103.07586v3-abstract-short" style="display: inline;"> Landau-Zener physics is often exploited to generate quantum logic gates and to perform state initialization and readout. The quality of these operations can be degraded by noise fluctuations in the energy gap at the avoided crossing. We leverage a recently discovered correspondence between qubit evolution and space curves in three dimensions to design noise-robust Landau-Zener sweeps through an av… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.07586v3-abstract-full').style.display = 'inline'; document.getElementById('2103.07586v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.07586v3-abstract-full" style="display: none;"> Landau-Zener physics is often exploited to generate quantum logic gates and to perform state initialization and readout. The quality of these operations can be degraded by noise fluctuations in the energy gap at the avoided crossing. We leverage a recently discovered correspondence between qubit evolution and space curves in three dimensions to design noise-robust Landau-Zener sweeps through an avoided crossing. In the case where the avoided crossing is purely noise-induced, we prove that operations based on monotonic sweeps cannot be robust to noise. Hence, we design families of phase gates based on non-monotonic drives that are error-robust up to second order. In the general case where there is an avoided crossing even in the absence of noise, we present a general technique for designing robust driving protocols that takes advantage of a relationship between the Landau-Zener problem and space curves of constant torsion. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.07586v3-abstract-full').style.display = 'none'; document.getElementById('2103.07586v3-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 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 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">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages, 11 figures; v3: final published version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum 6, 639 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.10017">arXiv:2101.10017</a> <span> [<a href="https://arxiv.org/pdf/2101.10017">pdf</a>, <a href="https://arxiv.org/format/2101.10017">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"> SpinQ Gemini: a desktop quantum computer for education and research </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Hou%2C+S">Shi-Yao Hou</a>, <a href="/search/quant-ph?searchtype=author&query=Feng%2C+G">Guanru Feng</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+Z">Zipeng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Zou%2C+H">Hongyang Zou</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+W">Wei Shi</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jinfeng Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+S">Sheng Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Sheng%2C+Z">Zikai Sheng</a>, <a href="/search/quant-ph?searchtype=author&query=Rao%2C+X">Xin Rao</a>, <a href="/search/quant-ph?searchtype=author&query=Ren%2C+B">Bing Ren</a>, <a href="/search/quant-ph?searchtype=author&query=Lu%2C+D">Dawei Lu</a>, <a href="/search/quant-ph?searchtype=author&query=Zou%2C+J">Junting Zou</a>, <a href="/search/quant-ph?searchtype=author&query=Miao%2C+G">Guoxing Miao</a>, <a href="/search/quant-ph?searchtype=author&query=Xiang%2C+J">Jingen Xiang</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+B">Bei Zeng</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="2101.10017v2-abstract-short" style="display: inline;"> SpinQ Gemini is a commercial desktop quantum computer designed and manufactured by SpinQ Technology. It is an integrated hardware-software system. The first generation product with two qubits was launched in January 2020. The hardware is based on NMR spectrometer, with permanent magnets providing $\sim 1$ T magnetic field. SpinQ Gemini operates under room temperature ($0$-$30^{\circ}$C), highlight… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.10017v2-abstract-full').style.display = 'inline'; document.getElementById('2101.10017v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.10017v2-abstract-full" style="display: none;"> SpinQ Gemini is a commercial desktop quantum computer designed and manufactured by SpinQ Technology. It is an integrated hardware-software system. The first generation product with two qubits was launched in January 2020. The hardware is based on NMR spectrometer, with permanent magnets providing $\sim 1$ T magnetic field. SpinQ Gemini operates under room temperature ($0$-$30^{\circ}$C), highlighting its lightweight (55 kg with a volume of $70\times 40 \times 80$ cm$^3$), cost-effective (under $50$k USD), and maintenance-free. SpinQ Gemini aims to provide real-device experience for quantum computing education for K-12 and at the college level. It also features quantum control design capabilities that benefit the researchers studying quantum control and quantum noise. Since its first launch, SpinQ Gemini has been shipped to institutions in Canada, Taiwan and Mainland China. This paper introduces the system of design of SpinQ Gemini, from hardware to software. We also demonstrate examples for performing quantum computing tasks on SpinQ Gemini, including one task for a variational quantum eigensolver of a two-qubit Heisenberg model. The next generations of SpinQ quantum computing devices will adopt models of more qubits, advanced control functions for researchers with comparable cost, as well as simplified models for much lower cost (under $5$k USD) for K-12 education. We believe that low-cost portable quantum computer products will facilitate hands-on experience for teaching quantum computing at all levels, well-prepare younger generations of students and researchers for the future of quantum technologies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.10017v2-abstract-full').style.display = 'none'; document.getElementById('2101.10017v2-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 February, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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, 17 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/2012.03819">arXiv:2012.03819</a> <span> [<a href="https://arxiv.org/pdf/2012.03819">pdf</a>, <a href="https://arxiv.org/format/2012.03819">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="Emerging Technologies">cs.ET</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computational Finance">q-fin.CP</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-2021-06-01-463">10.22331/q-2021-06-01-463 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Threshold for Quantum Advantage in Derivative Pricing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Chakrabarti%2C+S">Shouvanik Chakrabarti</a>, <a href="/search/quant-ph?searchtype=author&query=Krishnakumar%2C+R">Rajiv Krishnakumar</a>, <a href="/search/quant-ph?searchtype=author&query=Mazzola%2C+G">Guglielmo Mazzola</a>, <a href="/search/quant-ph?searchtype=author&query=Stamatopoulos%2C+N">Nikitas Stamatopoulos</a>, <a href="/search/quant-ph?searchtype=author&query=Woerner%2C+S">Stefan Woerner</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2012.03819v3-abstract-short" style="display: inline;"> We give an upper bound on the resources required for valuable quantum advantage in pricing derivatives. To do so, we give the first complete resource estimates for useful quantum derivative pricing, using autocallable and Target Accrual Redemption Forward (TARF) derivatives as benchmark use cases. We uncover blocking challenges in known approaches and introduce a new method for quantum derivative… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.03819v3-abstract-full').style.display = 'inline'; document.getElementById('2012.03819v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2012.03819v3-abstract-full" style="display: none;"> We give an upper bound on the resources required for valuable quantum advantage in pricing derivatives. To do so, we give the first complete resource estimates for useful quantum derivative pricing, using autocallable and Target Accrual Redemption Forward (TARF) derivatives as benchmark use cases. We uncover blocking challenges in known approaches and introduce a new method for quantum derivative pricing - the re-parameterization method - that avoids them. This method combines pre-trained variational circuits with fault-tolerant quantum computing to dramatically reduce resource requirements. We find that the benchmark use cases we examine require 8k logical qubits and a T-depth of 54 million. We estimate that quantum advantage would require executing this program at the order of a second. While the resource requirements given here are out of reach of current systems, we hope they will provide a roadmap for further improvements in algorithms, implementations, and planned hardware architectures. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.03819v3-abstract-full').style.display = 'none'; document.getElementById('2012.03819v3-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 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 December, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">Version to be published at Quantum</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum 5, 463 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2010.14821">arXiv:2010.14821</a> <span> [<a href="https://arxiv.org/pdf/2010.14821">pdf</a>, <a href="https://arxiv.org/format/2010.14821">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/10.1002/que2.77">10.1002/que2.77 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Simulating noisy variational quantum eigensolver with local noise models </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jinfeng Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+Z">Zipeng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+C">Chao Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Hou%2C+S">Shiyao Hou</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+P">Pengxiang Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+B">Bei Zeng</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="2010.14821v2-abstract-short" style="display: inline;"> Variational quantum eigensolver (VQE) is promising to show quantum advantage on near-term noisy-intermediate-scale quantum (NISQ) computers. One central problem of VQE is the effect of noise, especially the physical noise on realistic quantum computers. We study systematically the effect of noise for the VQE algorithm, by performing numerical simulations with various local noise models, including… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.14821v2-abstract-full').style.display = 'inline'; document.getElementById('2010.14821v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2010.14821v2-abstract-full" style="display: none;"> Variational quantum eigensolver (VQE) is promising to show quantum advantage on near-term noisy-intermediate-scale quantum (NISQ) computers. One central problem of VQE is the effect of noise, especially the physical noise on realistic quantum computers. We study systematically the effect of noise for the VQE algorithm, by performing numerical simulations with various local noise models, including the amplitude damping, dephasing, and depolarizing noise. We show that the ground state energy will deviate from the exact value as the noise probability increase and normally noise will accumulate as the circuit depth increase. We build a noise model to capture the noise in a real quantum computer. Our numerical simulation is consistent with the quantum experiment results on IBM Quantum computers through Cloud. Our work sheds new light on the practical research of noisy VQE. The deep understanding of the noise effect of VQE may help to develop quantum error mitigation techniques on near team quantum computers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.14821v2-abstract-full').style.display = 'none'; document.getElementById('2010.14821v2-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 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 October, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">9 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum Engineering.(2021) 1-14 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2009.04417">arXiv:2009.04417</a> <span> [<a href="https://arxiv.org/pdf/2009.04417">pdf</a>, <a href="https://arxiv.org/format/2009.04417">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="Emerging Technologies">cs.ET</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-2022-08-11-774">10.22331/q-2022-08-11-774 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Mitiq: A software package for error mitigation on noisy quantum computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=LaRose%2C+R">Ryan LaRose</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Kaiser%2C+S">Sarah Kaiser</a>, <a href="/search/quant-ph?searchtype=author&query=Karalekas%2C+P+J">Peter J. Karalekas</a>, <a href="/search/quant-ph?searchtype=author&query=Alves%2C+A+A">Andre A. Alves</a>, <a href="/search/quant-ph?searchtype=author&query=Czarnik%2C+P">Piotr Czarnik</a>, <a href="/search/quant-ph?searchtype=author&query=Mandouh%2C+M+E">Mohamed El Mandouh</a>, <a href="/search/quant-ph?searchtype=author&query=Gordon%2C+M+H">Max H. Gordon</a>, <a href="/search/quant-ph?searchtype=author&query=Hindy%2C+Y">Yousef Hindy</a>, <a href="/search/quant-ph?searchtype=author&query=Robertson%2C+A">Aaron Robertson</a>, <a href="/search/quant-ph?searchtype=author&query=Thakre%2C+P">Purva Thakre</a>, <a href="/search/quant-ph?searchtype=author&query=Wahl%2C+M">Misty Wahl</a>, <a href="/search/quant-ph?searchtype=author&query=Samuel%2C+D">Danny Samuel</a>, <a href="/search/quant-ph?searchtype=author&query=Mistri%2C+R">Rahul Mistri</a>, <a href="/search/quant-ph?searchtype=author&query=Tremblay%2C+M">Maxime Tremblay</a>, <a href="/search/quant-ph?searchtype=author&query=Gardner%2C+N">Nick Gardner</a>, <a href="/search/quant-ph?searchtype=author&query=Stemen%2C+N+T">Nathaniel T. Stemen</a>, <a href="/search/quant-ph?searchtype=author&query=Shammah%2C+N">Nathan Shammah</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2009.04417v4-abstract-short" style="display: inline;"> We introduce Mitiq, a Python package for error mitigation on noisy quantum computers. Error mitigation techniques can reduce the impact of noise on near-term quantum computers with minimal overhead in quantum resources by relying on a mixture of quantum sampling and classical post-processing techniques. Mitiq is an extensible toolkit of different error mitigation methods, including zero-noise extr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2009.04417v4-abstract-full').style.display = 'inline'; document.getElementById('2009.04417v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2009.04417v4-abstract-full" style="display: none;"> We introduce Mitiq, a Python package for error mitigation on noisy quantum computers. Error mitigation techniques can reduce the impact of noise on near-term quantum computers with minimal overhead in quantum resources by relying on a mixture of quantum sampling and classical post-processing techniques. Mitiq is an extensible toolkit of different error mitigation methods, including zero-noise extrapolation, probabilistic error cancellation, and Clifford data regression. The library is designed to be compatible with generic backends and interfaces with different quantum software frameworks. We describe Mitiq using code snippets to demonstrate usage and discuss features and contribution guidelines. We present several examples demonstrating error mitigation on IBM and Rigetti superconducting quantum processors as well as on noisy simulators. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2009.04417v4-abstract-full').style.display = 'none'; document.getElementById('2009.04417v4-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, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 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">33 pages, 8 figures. The Mitiq GitHub is https://github.com/unitaryfund/mitiq and the Mitiq documentation is https://mitiq.readthedocs.io/en/stable/</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum 6, 774 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2008.09854">arXiv:2008.09854</a> <span> [<a href="https://arxiv.org/pdf/2008.09854">pdf</a>, <a href="https://arxiv.org/format/2008.09854">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/10.1088/2058-9565/ac11a7">10.1088/2058-9565/ac11a7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A variational quantum algorithm for Hamiltonian diagonalization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jinfeng Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+C">Chao Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+P">Pengxiang Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+B">Bei Zeng</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="2008.09854v3-abstract-short" style="display: inline;"> Hamiltonian diagonalization is at the heart of understanding physical properties and practical applications of quantum systems. It is highly desired to design quantum algorithms that can speedup Hamiltonian diagonalization, especially those can be implemented on near-term quantum devices. In this work, we propose a variational algorithm for Hamiltonians diagonalization (VQHD) of quantum systems, w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2008.09854v3-abstract-full').style.display = 'inline'; document.getElementById('2008.09854v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2008.09854v3-abstract-full" style="display: none;"> Hamiltonian diagonalization is at the heart of understanding physical properties and practical applications of quantum systems. It is highly desired to design quantum algorithms that can speedup Hamiltonian diagonalization, especially those can be implemented on near-term quantum devices. In this work, we propose a variational algorithm for Hamiltonians diagonalization (VQHD) of quantum systems, which explores the important physical properties, such as temperature, locality and correlation, of the system. The key idea is that the thermal states of the system encode the information of eigenvalues and eigenstates of the system Hamiltonian. To obtain the full spectrum of the Hamiltonian, we use a quantum imaginary time evolution algorithm with high temperature, which prepares a thermal state with a small correlation length. With Trotterization, this then allows us to implement each step of imaginary time evolution by a local unitary transformation on only a small number of sites. Diagonalizing these thermal states hence leads to a full knowledge of the Hamiltonian eigensystem. We apply our algorithm to diagonalize local Hamiltonians and return results with high precision. Our VQHD algorithm sheds new light on the applications of near-term quantum computers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2008.09854v3-abstract-full').style.display = 'none'; document.getElementById('2008.09854v3-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 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 August, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">9 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum Sci. Technol. 6 (2021) 045009 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2005.10921">arXiv:2005.10921</a> <span> [<a href="https://arxiv.org/pdf/2005.10921">pdf</a>, <a href="https://arxiv.org/format/2005.10921">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/10.1109/QCE49297.2020.00045">10.1109/QCE49297.2020.00045 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Digital zero noise extrapolation for quantum error mitigation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Giurgica-Tiron%2C+T">Tudor Giurgica-Tiron</a>, <a href="/search/quant-ph?searchtype=author&query=Hindy%2C+Y">Yousef Hindy</a>, <a href="/search/quant-ph?searchtype=author&query=LaRose%2C+R">Ryan LaRose</a>, <a href="/search/quant-ph?searchtype=author&query=Mari%2C+A">Andrea Mari</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">William J. Zeng</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="2005.10921v2-abstract-short" style="display: inline;"> Zero-noise extrapolation (ZNE) is an increasingly popular technique for mitigating errors in noisy quantum computations without using additional quantum resources. We review the fundamentals of ZNE and propose several improvements to noise scaling and extrapolation, the two key components in the technique. We introduce unitary folding and parameterized noise scaling. These are digital noise scalin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.10921v2-abstract-full').style.display = 'inline'; document.getElementById('2005.10921v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2005.10921v2-abstract-full" style="display: none;"> Zero-noise extrapolation (ZNE) is an increasingly popular technique for mitigating errors in noisy quantum computations without using additional quantum resources. We review the fundamentals of ZNE and propose several improvements to noise scaling and extrapolation, the two key components in the technique. We introduce unitary folding and parameterized noise scaling. These are digital noise scaling frameworks, i.e. one can apply them using only gate-level access common to most quantum instruction sets. We also study different extrapolation methods, including a new adaptive protocol that uses a statistical inference framework. Benchmarks of our techniques show error reductions of 18X to 24X over non-mitigated circuits and demonstrate ZNE effectiveness at larger qubit numbers than have been tested previously. In addition to presenting new results, this work is a self-contained introduction to the practical use of ZNE by quantum programmers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.10921v2-abstract-full').style.display = 'none'; document.getElementById('2005.10921v2-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 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 May, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">11 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2020 IEEE International Conference on Quantum Computing and Engineering (QCE), Denver, CO, USA, 2020 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.09781">arXiv:1909.09781</a> <span> [<a href="https://arxiv.org/pdf/1909.09781">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Pattern Formation and Solitons">nlin.PS</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Gases">cond-mat.quant-gas</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Optics">physics.optics</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/10.1117/1.AP.1.4.046004">10.1117/1.AP.1.4.046004 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gap-type dark localized modes in a Bose-Einstein condensate with optical lattices </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+L">Liangwei Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jianhua Zeng</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="1909.09781v1-abstract-short" style="display: inline;"> Bose-Einstein condensate (BEC) exhibits a variety of fascinating and unexpected macroscopic phenomena, and has attracted sustained attention in recent years--particularly in the field of solitons and associated nonlinear phenomena. Meanwhile, optical lattices have emerged as a versatile toolbox for understanding the properties and controlling the dynamics of BEC, among which the realization of bri… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.09781v1-abstract-full').style.display = 'inline'; document.getElementById('1909.09781v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.09781v1-abstract-full" style="display: none;"> Bose-Einstein condensate (BEC) exhibits a variety of fascinating and unexpected macroscopic phenomena, and has attracted sustained attention in recent years--particularly in the field of solitons and associated nonlinear phenomena. Meanwhile, optical lattices have emerged as a versatile toolbox for understanding the properties and controlling the dynamics of BEC, among which the realization of bright gap solitons is an iconic result. However, the dark gap solitons are still experimentally unproven, and their properties in more than one dimension remain unknown. In light of this, we describe, numerically and theoretically, the formation and stability properties of gap-type dark localized modes in the context of ultracold atoms trapped in optical lattices. Two kinds of stable dark localized modes--gap solitons and soliton clusters--are predicted in both the one- and two-dimensional geometries. The vortical counterparts of both modes are also constructed in two dimensions. A unique feature is the existence of a nonlinear Bloch-wave background on which all above gap modes are situated. By employing linear-stability analysis and direct simulations, stability regions of the predicted modes are obtained. Our results offer the possibility of observing dark gap localized structures with cutting-edge techniques in ultracold atoms experiments and beyond, including in optics with photonic crystals and lattices. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.09781v1-abstract-full').style.display = 'none'; document.getElementById('1909.09781v1-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> 21 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">10 pages, 6 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Advanced Photonics 1,046004 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1811.04864">arXiv:1811.04864</a> <span> [<a href="https://arxiv.org/pdf/1811.04864">pdf</a>, <a href="https://arxiv.org/format/1811.04864">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> </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.99.052321">10.1103/PhysRevA.99.052321 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Geometric formalism for constructing arbitrary single-qubit dynamically corrected gates </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Yang%2C+C+H">C. H. Yang</a>, <a href="/search/quant-ph?searchtype=author&query=Dzurak%2C+A+S">A. S. Dzurak</a>, <a href="/search/quant-ph?searchtype=author&query=Barnes%2C+E">Edwin Barnes</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="1811.04864v2-abstract-short" style="display: inline;"> Implementing high-fidelity quantum control and reducing the effect of the coupling between a quantum system and its environment is a major challenge in developing quantum information technologies. Here, we show that there exists a geometrical structure hidden within the time-dependent Schr枚dinger equation that provides a simple way to view the entire solution space of pulses that suppress noise er… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.04864v2-abstract-full').style.display = 'inline'; document.getElementById('1811.04864v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1811.04864v2-abstract-full" style="display: none;"> Implementing high-fidelity quantum control and reducing the effect of the coupling between a quantum system and its environment is a major challenge in developing quantum information technologies. Here, we show that there exists a geometrical structure hidden within the time-dependent Schr枚dinger equation that provides a simple way to view the entire solution space of pulses that suppress noise errors in a system's evolution. In this framework, any single-qubit gate that is robust against quasistatic noise to first order corresponds to a closed three-dimensional space curve, where the driving fields that implement the robust gate can be read off from the curvature and torsion of the space curve. Gates that are robust to second order are in one-to-one correspondence with closed curves whose projections onto three mutually orthogonal planes each enclose a vanishing net area. We use this formalism to derive new examples of dynamically corrected gates generated from smooth pulses. We also show how it can be employed to analyze the noise-cancellation properties of pulses generated from numerical algorithms such as GRAPE. A similar geometrical framework exists for quantum systems of arbitrary Hilbert space dimension. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.04864v2-abstract-full').style.display = 'none'; document.getElementById('1811.04864v2-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> 13 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 November, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">published version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. A 99, 052321 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1808.03425">arXiv:1808.03425</a> <span> [<a href="https://arxiv.org/pdf/1808.03425">pdf</a>, <a href="https://arxiv.org/format/1808.03425">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="Machine Learning">cs.LG</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Machine Learning">stat.ML</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.99.052306">10.1103/PhysRevA.99.052306 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Learning and Inference on Generative Adversarial Quantum Circuits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jinfeng Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+Y">Yufeng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Liu%2C+J">Jin-Guo Liu</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+L">Lei Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Hu%2C+J">Jiangping Hu</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="1808.03425v1-abstract-short" style="display: inline;"> Quantum mechanics is inherently probabilistic in light of Born's rule. Using quantum circuits as probabilistic generative models for classical data exploits their superior expressibility and efficient direct sampling ability. However, training of quantum circuits can be more challenging compared to classical neural networks due to lack of efficient differentiable learning algorithm. We devise an a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1808.03425v1-abstract-full').style.display = 'inline'; document.getElementById('1808.03425v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1808.03425v1-abstract-full" style="display: none;"> Quantum mechanics is inherently probabilistic in light of Born's rule. Using quantum circuits as probabilistic generative models for classical data exploits their superior expressibility and efficient direct sampling ability. However, training of quantum circuits can be more challenging compared to classical neural networks due to lack of efficient differentiable learning algorithm. We devise an adversarial quantum-classical hybrid training scheme via coupling a quantum circuit generator and a classical neural network discriminator together. After training, the quantum circuit generative model can infer missing data with quadratic speed up via amplitude amplification. We numerically simulate the learning and inference of generative adversarial quantum circuit using the prototypical Bars-and-Stripes dataset. Generative adversarial quantum circuits is a fresh approach to machine learning which may enjoy the practically useful quantum advantage on near-term quantum devices. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1808.03425v1-abstract-full').style.display = 'none'; document.getElementById('1808.03425v1-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 August, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">7 pages, 6 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 99, 052306 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1806.05550">arXiv:1806.05550</a> <span> [<a href="https://arxiv.org/pdf/1806.05550">pdf</a>, <a href="https://arxiv.org/ps/1806.05550">ps</a>, <a href="https://arxiv.org/format/1806.05550">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"> Simulating Dirac equation with Josephson junction circuits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Ji%2C+X+h">Xiao hui Ji</a>, <a href="/search/quant-ph?searchtype=author&query=Lin%2C+W+b">Wen bin Lin</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J+g">Jia gang Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=di+Wang%2C+G">Guang di Wang</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="1806.05550v1-abstract-short" style="display: inline;"> We propose a scheme for simulating 3+1, 2+1, 1+1 Dirac equation for a free spin-1/2 particle with superconducting josephson circuits consisting of five qubits, four qubits, two qubits respectively. In 3+1D and 2+1D, the flux qubit1 driven by a resonant pulse is in the superposition state of its own two eigenstatesis, and it is used as a bus to induce the (blue)red-sideband excitation consisting of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.05550v1-abstract-full').style.display = 'inline'; document.getElementById('1806.05550v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1806.05550v1-abstract-full" style="display: none;"> We propose a scheme for simulating 3+1, 2+1, 1+1 Dirac equation for a free spin-1/2 particle with superconducting josephson circuits consisting of five qubits, four qubits, two qubits respectively. In 3+1D and 2+1D, the flux qubit1 driven by a resonant pulse is in the superposition state of its own two eigenstatesis, and it is used as a bus to induce the (blue)red-sideband excitation consisting of a magnetic pulse acting resonantly on two levels of the flux qubit2 and the energy levels of one phase qubit, which yields two (Anti)Jaynes-Cummings interactions with one driving pulse and reduces the damage of the driving pulses to the system consequently. Numerical results show that decoherence time is several times longer than transition time supposing set appropriate experimental parameters. Therefore experiments verifying the dynamics of electron and neutrino, such as Zitterberwung effect in 3+1, 2+1 and 1+1 dimensions, can be implemented by microelectronic chips composed of the qubits as artificial atoms. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.05550v1-abstract-full').style.display = 'none'; document.getElementById('1806.05550v1-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> 13 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2018. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1802.10241">arXiv:1802.10241</a> <span> [<a href="https://arxiv.org/pdf/1802.10241">pdf</a>, <a href="https://arxiv.org/format/1802.10241">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> </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.98.012301">10.1103/PhysRevA.98.012301 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The fastest pulses that implement dynamically corrected gates </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Barnes%2C+E">Edwin Barnes</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="1802.10241v2-abstract-short" style="display: inline;"> Dynamically correcting for unwanted interactions between a quantum system and its environment is vital to achieving the high-fidelity quantum control necessary for a broad range of quantum information technologies. In recent work, we uncovered the complete solution space of all possible driving fields that suppress transverse quasistatic noise errors while performing single-qubit operations. This… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1802.10241v2-abstract-full').style.display = 'inline'; document.getElementById('1802.10241v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1802.10241v2-abstract-full" style="display: none;"> Dynamically correcting for unwanted interactions between a quantum system and its environment is vital to achieving the high-fidelity quantum control necessary for a broad range of quantum information technologies. In recent work, we uncovered the complete solution space of all possible driving fields that suppress transverse quasistatic noise errors while performing single-qubit operations. This solution space lives within a simple geometrical framework that makes it possible to obtain globally optimal pulses subject to a set of experimental constraints by solving certain geometrical optimization problems. In this work, we solve such a geometrical optimization problem to find the fastest possible pulses that implement single-qubit gates while cancelling transverse quasistatic noise to second order. Because the time-optimized pulses are not smooth, we provide a method based on our geometrical approach to obtain experimentally feasible smooth pulses that approximate the time-optimal ones with minimal loss in gate speed. We show that in the presence of realistic constraints on pulse rise times, our smooth pulses significantly outperform sequences based on ideal pulse shapes, highlighting the benefits of building experimental waveform constraints directly into dynamically corrected gate designs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1802.10241v2-abstract-full').style.display = 'none'; document.getElementById('1802.10241v2-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 March, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 February, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">10 pages, 9 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, 012301 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1801.02804">arXiv:1801.02804</a> <span> [<a href="https://arxiv.org/pdf/1801.02804">pdf</a>, <a href="https://arxiv.org/ps/1801.02804">ps</a>, <a href="https://arxiv.org/format/1801.02804">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"> Spontaneous emission of a moving atom in a waveguide of rectangular cross section </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jing Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Lu%2C+J">Jing Lu</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+L">Lan Zhou</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="1801.02804v1-abstract-short" style="display: inline;"> We study the spontaneous emission (SE) of an excited two-level nonrelativistic system (TLS) interacting with the vacuum in a waveguide of rectangular cross section. All TLS's transitions and the center-of-mass motion of the TLS are taken into account. The SE rate and the carried frequency of the emitted photon for the TLS initial being at rest is obtained, it is found in the first order of the cen… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.02804v1-abstract-full').style.display = 'inline'; document.getElementById('1801.02804v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1801.02804v1-abstract-full" style="display: none;"> We study the spontaneous emission (SE) of an excited two-level nonrelativistic system (TLS) interacting with the vacuum in a waveguide of rectangular cross section. All TLS's transitions and the center-of-mass motion of the TLS are taken into account. The SE rate and the carried frequency of the emitted photon for the TLS initial being at rest is obtained, it is found in the first order of the center of mass (c.m.) that the frequency of the emitted photon could be smaller or larger than the transition frequency of the TLS but the SE rate is smaller than the SE rate $螕_{f}$ of the TLS fixed in the same waveguide. The SE rate and the carried frequency of the emitted photon for the TLS initial being moving is also obtained in the first order of the c.m.. The SE rate is larger than $螕_{f}$ but it is independent of the initial momentum. The carried frequency of the emitted photon is creased when it travels along the direction of the initial momentum and is decreased when it travels in the opposite direction of the initial momentum. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.02804v1-abstract-full').style.display = 'none'; document.getElementById('1801.02804v1-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> 9 January, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2018. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1712.05771">arXiv:1712.05771</a> <span> [<a href="https://arxiv.org/pdf/1712.05771">pdf</a>, <a href="https://arxiv.org/format/1712.05771">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"> Unsupervised Machine Learning on a Hybrid Quantum Computer </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Otterbach%2C+J+S">J. S. Otterbach</a>, <a href="/search/quant-ph?searchtype=author&query=Manenti%2C+R">R. Manenti</a>, <a href="/search/quant-ph?searchtype=author&query=Alidoust%2C+N">N. Alidoust</a>, <a href="/search/quant-ph?searchtype=author&query=Bestwick%2C+A">A. Bestwick</a>, <a href="/search/quant-ph?searchtype=author&query=Block%2C+M">M. Block</a>, <a href="/search/quant-ph?searchtype=author&query=Bloom%2C+B">B. Bloom</a>, <a href="/search/quant-ph?searchtype=author&query=Caldwell%2C+S">S. Caldwell</a>, <a href="/search/quant-ph?searchtype=author&query=Didier%2C+N">N. Didier</a>, <a href="/search/quant-ph?searchtype=author&query=Fried%2C+E+S">E. Schuyler Fried</a>, <a href="/search/quant-ph?searchtype=author&query=Hong%2C+S">S. Hong</a>, <a href="/search/quant-ph?searchtype=author&query=Karalekas%2C+P">P. Karalekas</a>, <a href="/search/quant-ph?searchtype=author&query=Osborn%2C+C+B">C. B. Osborn</a>, <a href="/search/quant-ph?searchtype=author&query=Papageorge%2C+A">A. Papageorge</a>, <a href="/search/quant-ph?searchtype=author&query=Peterson%2C+E+C">E. C. Peterson</a>, <a href="/search/quant-ph?searchtype=author&query=Prawiroatmodjo%2C+G">G. Prawiroatmodjo</a>, <a href="/search/quant-ph?searchtype=author&query=Rubin%2C+N">N. Rubin</a>, <a href="/search/quant-ph?searchtype=author&query=Ryan%2C+C+A">Colm A. Ryan</a>, <a href="/search/quant-ph?searchtype=author&query=Scarabelli%2C+D">D. Scarabelli</a>, <a href="/search/quant-ph?searchtype=author&query=Scheer%2C+M">M. Scheer</a>, <a href="/search/quant-ph?searchtype=author&query=Sete%2C+E+A">E. A. Sete</a>, <a href="/search/quant-ph?searchtype=author&query=Sivarajah%2C+P">P. Sivarajah</a>, <a href="/search/quant-ph?searchtype=author&query=Smith%2C+R+S">Robert S. Smith</a>, <a href="/search/quant-ph?searchtype=author&query=Staley%2C+A">A. Staley</a>, <a href="/search/quant-ph?searchtype=author&query=Tezak%2C+N">N. Tezak</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+W+J">W. J. Zeng</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="1712.05771v1-abstract-short" style="display: inline;"> Machine learning techniques have led to broad adoption of a statistical model of computing. The statistical distributions natively available on quantum processors are a superset of those available classically. Harnessing this attribute has the potential to accelerate or otherwise improve machine learning relative to purely classical performance. A key challenge toward that goal is learning to hybr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.05771v1-abstract-full').style.display = 'inline'; document.getElementById('1712.05771v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1712.05771v1-abstract-full" style="display: none;"> Machine learning techniques have led to broad adoption of a statistical model of computing. The statistical distributions natively available on quantum processors are a superset of those available classically. Harnessing this attribute has the potential to accelerate or otherwise improve machine learning relative to purely classical performance. A key challenge toward that goal is learning to hybridize classical computing resources and traditional learning techniques with the emerging capabilities of general purpose quantum processors. Here, we demonstrate such hybridization by training a 19-qubit gate model processor to solve a clustering problem, a foundational challenge in unsupervised learning. We use the quantum approximate optimization algorithm in conjunction with a gradient-free Bayesian optimization to train the quantum machine. This quantum/classical hybrid algorithm shows robustness to realistic noise, and we find evidence that classical optimization can be used to train around both coherent and incoherent imperfections. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.05771v1-abstract-full').style.display = 'none'; document.getElementById('1712.05771v1-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 December, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">7 pages + appendix, many 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/1705.01761">arXiv:1705.01761</a> <span> [<a href="https://arxiv.org/pdf/1705.01761">pdf</a>, <a href="https://arxiv.org/ps/1705.01761">ps</a>, <a href="https://arxiv.org/format/1705.01761">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Pattern Formation and Solitons">nlin.PS</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Optics">physics.optics</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/PhysRevE.95.052214">10.1103/PhysRevE.95.052214 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Localized dark solitons and vortices in defocusing media with spatially inhomogeneous nonlinearity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Jianhua Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Malomed%2C+B+A">Boris A. Malomed</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="1705.01761v1-abstract-short" style="display: inline;"> Recent studies have demonstrated that defocusing cubic nonlinearity with local strength growing from the center to the periphery faster than $r^{D}$, in space of dimension $D$ with radial coordinate $r$, supports a vast variety of robust bright solitons. In the framework of the same model, but with a weaker spatial-growth rate, $\sim r^{伪}$ with $伪\leq D$, we here test the possibility to create st… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.01761v1-abstract-full').style.display = 'inline'; document.getElementById('1705.01761v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1705.01761v1-abstract-full" style="display: none;"> Recent studies have demonstrated that defocusing cubic nonlinearity with local strength growing from the center to the periphery faster than $r^{D}$, in space of dimension $D$ with radial coordinate $r$, supports a vast variety of robust bright solitons. In the framework of the same model, but with a weaker spatial-growth rate, $\sim r^{伪}$ with $伪\leq D$, we here test the possibility to create stable\textit{\ localized continuous waves} (LCWs) in one- and two-dimensional (1D and 2D) geometries, \textit{% localized dark solitons} (LDSs) in 1D, and \textit{localized dark vortices} (LDVs) in 2D, which are all realized as loosely confined states with a divergent norm. Asymptotic tails of the solutions, which determine the divergence of the norm, are constructed in a universal analytical form by means of the Thomas-Fermi approximation (TFA). Global approximations for the LCWs, LDSs, and LDVs are constructed on the basis of interpolations between analytical approximations available far from (TFA) and close to the center. In particular, the interpolations for the 1D LDS, as well as for the 2D LDVs, are based on a \textquotedblleft deformed-tanh" expression, which is suggested by the usual 1D dark-soliton solution. In addition to the 1D fundamental LDSs with the single notch, and 2D vortices with $S=1$, higher-order LDSs with multiple notches are found too, as well as double LDVs, with $S=2$. Stability regions for the modes under the consideration are identified by means of systematic simulations, the LCWs being completely stable in 1D and 2D, as they are ground states in the corresponding settings. Basic evolution scenarios are identified for those vortices which are unstable. The settings considered in this work may be implemented in nonlinear optics and in Bose-Einstein condensates. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.01761v1-abstract-full').style.display = 'none'; document.getElementById('1705.01761v1-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> 4 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">9 pages,9 figures,Physical Review E, in press</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. E 95, 052214 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1703.00816">arXiv:1703.00816</a> <span> [<a href="https://arxiv.org/pdf/1703.00816">pdf</a>, <a href="https://arxiv.org/format/1703.00816">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="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/10.1088/1367-2630/aaafe9">10.1088/1367-2630/aaafe9 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> General solution to inhomogeneous dephasing and smooth pulse dynamical decoupling </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+J">Junkai Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+X">Xiu-Hao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Russo%2C+A">Antonio Russo</a>, <a href="/search/quant-ph?searchtype=author&query=Barnes%2C+E">Edwin Barnes</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="1703.00816v3-abstract-short" style="display: inline;"> In order to achieve the high-fidelity quantum control needed for a broad range of quantum information technologies, reducing the effects of noise and system inhomogeneities is an essential task. It is well known that a system can be decoupled from noise or made insensitive to inhomogeneous dephasing dynamically by using carefully designed pulse sequences based on square or delta-function waveforms… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1703.00816v3-abstract-full').style.display = 'inline'; document.getElementById('1703.00816v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1703.00816v3-abstract-full" style="display: none;"> In order to achieve the high-fidelity quantum control needed for a broad range of quantum information technologies, reducing the effects of noise and system inhomogeneities is an essential task. It is well known that a system can be decoupled from noise or made insensitive to inhomogeneous dephasing dynamically by using carefully designed pulse sequences based on square or delta-function waveforms such as Hahn spin echo or CPMG. However, such ideal pulses are often challenging to implement experimentally with high fidelity. Here, we uncover a new geometrical framework for visualizing all possible driving fields, which enables one to generate an unlimited number of smooth, experimentally feasible pulses that perform dynamical decoupling or dynamically corrected gates to arbitrarily high order. We demonstrate that this scheme can significantly enhance the fidelity of single-qubit operations in the presence of noise and when realistic limitations on pulse rise times and amplitudes are taken into account. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1703.00816v3-abstract-full').style.display = 'none'; document.getElementById('1703.00816v3-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 February, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 March, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">23 pages, 10 figures; v3: NJP version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> New J. 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