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is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Cao%2C+C&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Cao%2C+C&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Cao%2C+C&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.07296">arXiv:2411.07296</a> <span> [<a href="https://arxiv.org/pdf/2411.07296">pdf</a>, <a href="https://arxiv.org/format/2411.07296">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</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"> Non-isometry, State-Dependence and Holography </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Antonini%2C+S">Stefano Antonini</a>, <a href="/search/quant-ph?searchtype=author&query=Balasubramanian%2C+V">Vijay Balasubramanian</a>, <a href="/search/quant-ph?searchtype=author&query=Bao%2C+N">Ning Bao</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Chemissany%2C+W">Wissam Chemissany</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.07296v1-abstract-short" style="display: inline;"> We establish an equivalence between non-isometry of quantum codes and state-dependence of operator reconstruction, and discuss implications of this equivalence for holographic duality. Specifically, we define quantitative measures of non-isometry and state-dependence and describe bounds relating these quantities. In the context of holography we show that, assuming known gravitational path integral… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.07296v1-abstract-full').style.display = 'inline'; document.getElementById('2411.07296v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.07296v1-abstract-full" style="display: none;"> We establish an equivalence between non-isometry of quantum codes and state-dependence of operator reconstruction, and discuss implications of this equivalence for holographic duality. Specifically, we define quantitative measures of non-isometry and state-dependence and describe bounds relating these quantities. In the context of holography we show that, assuming known gravitational path integral results for overlaps between semiclassical states, non-isometric bulk-to-boundary maps with a trivial kernel are approximately isometric and bulk reconstruction approximately state-independent. In contrast, non-isometric maps with a non-empty kernel always lead to state-dependent reconstruction. We also show that if a global bulk-to-boundary map is non-isometric, then there exists a region in the bulk which is causally disconnected from the boundary. Finally, we conjecture that, under certain physical assumptions for the definition of the Hilbert space of effective field theory in AdS space, the presence of a global horizon implies a non-isometric global bulk-to-boundary map. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.07296v1-abstract-full').style.display = 'none'; document.getElementById('2411.07296v1-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, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">35 pages, 1 figure + Appendices</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.22861">arXiv:2410.22861</a> <span> [<a href="https://arxiv.org/pdf/2410.22861">pdf</a>, <a href="https://arxiv.org/format/2410.22861">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"> LEGO_HQEC: A Software Tool for Analyzing Holographic Quantum Codes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Fan%2C+J">Junyu Fan</a>, <a href="/search/quant-ph?searchtype=author&query=Steinberg%2C+M">Matthew Steinberg</a>, <a href="/search/quant-ph?searchtype=author&query=Jahn%2C+A">Alexander Jahn</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chunjun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Sarkar%2C+A">Aritra Sarkar</a>, <a href="/search/quant-ph?searchtype=author&query=Feld%2C+S">Sebastian Feld</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.22861v1-abstract-short" style="display: inline;"> Quantum error correction (QEC) is a crucial prerequisite for future large-scale quantum computation. Finding and analyzing new QEC codes, along with efficient decoding and fault-tolerance protocols, is central to this effort. Holographic codes are a recent class of QEC subsystem codes derived from holographic bulk/boundary dualities. In addition to exploring the physics of such dualities, these co… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.22861v1-abstract-full').style.display = 'inline'; document.getElementById('2410.22861v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.22861v1-abstract-full" style="display: none;"> Quantum error correction (QEC) is a crucial prerequisite for future large-scale quantum computation. Finding and analyzing new QEC codes, along with efficient decoding and fault-tolerance protocols, is central to this effort. Holographic codes are a recent class of QEC subsystem codes derived from holographic bulk/boundary dualities. In addition to exploring the physics of such dualities, these codes possess useful QEC properties such as tunable encoding rates, distance scaling competitive with topological codes, and excellent recovery thresholds. To allow for a comprehensive analysis of holographic code constructions, we introduce LEGO_HQEC, a software package utilizing the quantum LEGO formalism. This package constructs holographic codes on regular hyperbolic tilings and generates their stabilizer generators and logical operators for a specified number of seed codes and layers. Three decoders are included: an erasure decoder based on Gaussian elimination; an integer-optimization decoder; and a tensor-network decoder. With these tools, LEGO_HQEC thus enables future systematic studies regarding the utility of holographic codes for practical quantum computing. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.22861v1-abstract-full').style.display = 'none'; document.getElementById('2410.22861v1-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 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.06232">arXiv:2408.06232</a> <span> [<a href="https://arxiv.org/pdf/2408.06232">pdf</a>, <a href="https://arxiv.org/format/2408.06232">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="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Overcoming the Zero-Rate Hashing Bound with Holographic Quantum Error Correction </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Fan%2C+J">Junyu Fan</a>, <a href="/search/quant-ph?searchtype=author&query=Steinberg%2C+M">Matthew Steinberg</a>, <a href="/search/quant-ph?searchtype=author&query=Jahn%2C+A">Alexander Jahn</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Charles Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Feld%2C+S">Sebastian Feld</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="2408.06232v1-abstract-short" style="display: inline;"> Several recent techniques for modifying topological codes with single-qubit Clifford operators have shown high resilience against pure Pauli noise. Paramount to these findings has been the demonstration that several variants exhibit error thresholds often attaining or exceeding the zero-rate hashing bound, a known benchmark for code-capacity noise channels, for biased noise. Additionally, direct c… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.06232v1-abstract-full').style.display = 'inline'; document.getElementById('2408.06232v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.06232v1-abstract-full" style="display: none;"> Several recent techniques for modifying topological codes with single-qubit Clifford operators have shown high resilience against pure Pauli noise. Paramount to these findings has been the demonstration that several variants exhibit error thresholds often attaining or exceeding the zero-rate hashing bound, a known benchmark for code-capacity noise channels, for biased noise. Additionally, direct comparison with the hashing bound has shown that several topological codes outperform the hashing bound at points of finite Pauli noise biases. Motivated by these observations, we study zero-rate holographic quantum error correction codes, discovering very high threshold values under diverse and finitely-biased noise channels using a tensor-network decoding approach. Our results establish that all codes tested achieve or surpass the hashing bound at various points, ranging from pure 2-Pauli noise ($畏= 0$) to pure 1-Pauli noise ($畏= +\infty$), thereby demonstrating that holographic codes exhibit excellent error tolerance in the code-capacity picture. Such findings imply the existence of a structured and systematic method for constructing high-threshold codes suitable for realistically motivated noise channels. To our knowledge, this work is also the first instance of such remarkable threshold behavior in stabilizer quantum codes for the pure 2-Pauli noise regime, as well as for finitely-biased noise channels. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.06232v1-abstract-full').style.display = 'none'; document.getElementById('2408.06232v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, 5 figures, 2 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.09180">arXiv:2405.09180</a> <span> [<a href="https://arxiv.org/pdf/2405.09180">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Superconductivity">cond-mat.supr-con</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41467-024-48224-1">10.1038/s41467-024-48224-1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Integrated and DC-powered superconducting microcomb </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Wang%2C+C">Chen-Guang Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+W">Wuyue Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+C">Chong Li</a>, <a href="/search/quant-ph?searchtype=author&query=Shi%2C+L">Lili Shi</a>, <a href="/search/quant-ph?searchtype=author&query=Jiang%2C+J">Junliang Jiang</a>, <a href="/search/quant-ph?searchtype=author&query=Guo%2C+T">Tingting Guo</a>, <a href="/search/quant-ph?searchtype=author&query=Yue%2C+W">Wen-Cheng Yue</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+T">Tianyu Li</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+P">Ping Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Lyu%2C+Y">Yang-Yang Lyu</a>, <a href="/search/quant-ph?searchtype=author&query=Pan%2C+J">Jiazheng Pan</a>, <a href="/search/quant-ph?searchtype=author&query=Deng%2C+X">Xiuhao Deng</a>, <a href="/search/quant-ph?searchtype=author&query=Dong%2C+Y">Ying Dong</a>, <a href="/search/quant-ph?searchtype=author&query=Tu%2C+X">Xuecou Tu</a>, <a href="/search/quant-ph?searchtype=author&query=Dong%2C+S">Sining Dong</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chunhai Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+L">Labao Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Jia%2C+X">Xiaoqing Jia</a>, <a href="/search/quant-ph?searchtype=author&query=Sun%2C+G">Guozhu Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Kang%2C+L">Lin Kang</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+J">Jian Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+Y">Yong-Lei Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+H">Huabing Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+P">Peiheng Wu</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="2405.09180v1-abstract-short" style="display: inline;"> Frequency combs, specialized laser sources emitting multiple equidistant frequency lines, have revolutionized science and technology with unprecedented precision and versatility. Recently, integrated frequency combs are emerging as scalable solutions for on-chip photonics. Here, we demonstrate a fully integrated superconducting microcomb that is easy to manufacture, simple to operate, and consumes… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.09180v1-abstract-full').style.display = 'inline'; document.getElementById('2405.09180v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.09180v1-abstract-full" style="display: none;"> Frequency combs, specialized laser sources emitting multiple equidistant frequency lines, have revolutionized science and technology with unprecedented precision and versatility. Recently, integrated frequency combs are emerging as scalable solutions for on-chip photonics. Here, we demonstrate a fully integrated superconducting microcomb that is easy to manufacture, simple to operate, and consumes ultra-low power. Our turnkey apparatus comprises a basic nonlinear superconducting device, a Josephson junction, directly coupled to a superconducting microstrip resonator. We showcase coherent comb generation through self-started mode-locking. Therefore, comb emission is initiated solely by activating a DC bias source, with power consumption as low as tens of picowatts. The resulting comb spectrum resides in the microwave domain and spans multiple octaves. The linewidths of all comb lines can be narrowed down to 1 Hz through a unique coherent injection-locking technique. Our work represents a critical step towards fully integrated microwave photonics and offers the potential for integrated quantum processors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.09180v1-abstract-full').style.display = 'none'; document.getElementById('2405.09180v1-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 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">Journal ref:</span> Nature Communications 15, 4009 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.08441">arXiv:2405.08441</a> <span> [<a href="https://arxiv.org/pdf/2405.08441">pdf</a>, <a href="https://arxiv.org/format/2405.08441">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Unveiling quantum phase transitions from traps in variational quantum algorithms </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Gambetta%2C+F+M">Filippo Maria Gambetta</a>, <a href="/search/quant-ph?searchtype=author&query=Montanaro%2C+A">Ashley Montanaro</a>, <a href="/search/quant-ph?searchtype=author&query=Santos%2C+R+A">Raul A. Santos</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="2405.08441v1-abstract-short" style="display: inline;"> Understanding quantum phase transitions in physical systems is fundamental to characterize their behaviour at small temperatures. Achieving this requires both accessing good approximations to the ground state and identifying order parameters to distinguish different phases. Addressing these challenges, our work introduces a hybrid algorithm that combines quantum optimization with classical machine… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.08441v1-abstract-full').style.display = 'inline'; document.getElementById('2405.08441v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.08441v1-abstract-full" style="display: none;"> Understanding quantum phase transitions in physical systems is fundamental to characterize their behaviour at small temperatures. Achieving this requires both accessing good approximations to the ground state and identifying order parameters to distinguish different phases. Addressing these challenges, our work introduces a hybrid algorithm that combines quantum optimization with classical machine learning. This approach leverages the capability of near-term quantum computers to prepare locally trapped states through finite optimization. Specifically, we utilize LASSO for identifying conventional phase transitions and the Transformer model for topological transitions, applying these with a sliding window of Hamiltonian parameters to learn appropriate order parameters and estimate the critical points accurately. We verified the effectiveness of our method with numerical simulation and real-hardware experiments on Rigetti's Ankaa 9Q-1 quantum computer. Our protocol not only provides a robust framework for investigating quantum phase transitions using shallow quantum circuits but also significantly enhances efficiency and precision, opening new avenues in the integration of quantum computing and machine learning. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.08441v1-abstract-full').style.display = 'none'; document.getElementById('2405.08441v1-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 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">19 pages, 9 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/2404.17560">arXiv:2404.17560</a> <span> [<a href="https://arxiv.org/pdf/2404.17560">pdf</a>, <a href="https://arxiv.org/format/2404.17560">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"> Exploiting many-body localization for scalable variational quantum simulation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+Y">Yeqing Zhou</a>, <a href="/search/quant-ph?searchtype=author&query=Tannu%2C+S">Swamit Tannu</a>, <a href="/search/quant-ph?searchtype=author&query=Shannon%2C+N">Nic Shannon</a>, <a href="/search/quant-ph?searchtype=author&query=Joynt%2C+R">Robert Joynt</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="2404.17560v2-abstract-short" style="display: inline;"> Variational quantum algorithms have emerged as a promising approach to achieving practical quantum advantages using near-term quantum devices. Despite their potential, the scalability of these algorithms poses a significant challenge. This is largely attributed to the "barren plateau" phenomenon, which persists even in the absence of noise. In this work, we explore the many-body localization (MBL)… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.17560v2-abstract-full').style.display = 'inline'; document.getElementById('2404.17560v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.17560v2-abstract-full" style="display: none;"> Variational quantum algorithms have emerged as a promising approach to achieving practical quantum advantages using near-term quantum devices. Despite their potential, the scalability of these algorithms poses a significant challenge. This is largely attributed to the "barren plateau" phenomenon, which persists even in the absence of noise. In this work, we explore the many-body localization (MBL)-thermalization phase transitions within a framework of Floquet-initialized variational quantum circuits and investigate how MBL could be used to avoid barren plateaus. The phase transitions are observed through calculations of the inverse participation ratio, the entanglement entropy, and a metric termed low-weight stabilizer R茅nyi entropy. By initializing the circuit in the MBL phase and employing an easily preparable initial state, we find it is possible to prevent the formation of a unitary 2-design, resulting in an output state with entanglement that follows an area- rather than a volume-law, and which circumvents barren plateaus throughout the optimization. Utilizing this methodology, we successfully determine the ground states of various model Hamiltonians across different phases and show that the resources required for the optimization are significantly reduced. We have further validated the MBL approach through experiments carried out on the 127-qubit $ibm\_brisbane$ quantum processor. These experiments confirm that the gradients needed to carry out variational calculations are restored in the MBL phase of a Heisenberg model subject to random unitary "kicks". These results provide new insights into the interplay between MBL and quantum computing, and suggest that the role of MBL states should be considered in the design of quantum algorithms. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.17560v2-abstract-full').style.display = 'none'; document.getElementById('2404.17560v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 April, 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">18 pages, 10 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/2403.07056">arXiv:2403.07056</a> <span> [<a href="https://arxiv.org/pdf/2403.07056">pdf</a>, <a href="https://arxiv.org/format/2403.07056">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</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"> Gravitational back-reaction is magical </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Cheng%2C+G">Gong Cheng</a>, <a href="/search/quant-ph?searchtype=author&query=Hamma%2C+A">Alioscia Hamma</a>, <a href="/search/quant-ph?searchtype=author&query=Leone%2C+L">Lorenzo Leone</a>, <a href="/search/quant-ph?searchtype=author&query=Munizzi%2C+W">William Munizzi</a>, <a href="/search/quant-ph?searchtype=author&query=Oliviero%2C+S+F+E">Savatore F. E. Oliviero</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2403.07056v2-abstract-short" style="display: inline;"> We study the interplay between magic and entanglement in quantum many-body systems. We show that non-local magic, which is supported by the quantum correlations is lower bounded by the non-flatness of entanglement spectrum and upper bounded by the amount of entanglement in the system. We then argue that a smoothed version of non-local magic bounds the hardness of classical simulations for incompre… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.07056v2-abstract-full').style.display = 'inline'; document.getElementById('2403.07056v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2403.07056v2-abstract-full" style="display: none;"> We study the interplay between magic and entanglement in quantum many-body systems. We show that non-local magic, which is supported by the quantum correlations is lower bounded by the non-flatness of entanglement spectrum and upper bounded by the amount of entanglement in the system. We then argue that a smoothed version of non-local magic bounds the hardness of classical simulations for incompressible states. In conformal field theories, we conjecture that the non-local magic should scale linearly with entanglement entropy but sublinearly when an approximation of the state is allowed. We support the conjectures using both analytical arguments based on unitary distillation and numerical data from an Ising CFT. If the CFT has a holographic dual, then we prove that the non-local magic vanishes if and only if there is no gravitational back-reaction. Furthermore, we show that non-local magic is approximately equal to the rate of change of the minimal surface area in response to the change of cosmic brane tension in the bulk. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.07056v2-abstract-full').style.display = 'none'; document.getElementById('2403.07056v2-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 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">62 pages, 20 figures; title changed, Theorem 1 and 2 refined, references added</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2310.19538">arXiv:2310.19538</a> <span> [<a href="https://arxiv.org/pdf/2310.19538">pdf</a>, <a href="https://arxiv.org/format/2310.19538">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 Lego and XP Stabilizer Codes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Shen%2C+R">Ruohan Shen</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+Y">Yixu Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</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="2310.19538v1-abstract-short" style="display: inline;"> We apply the recent graphical framework of ''quantum lego'' to XP stabilizer codes where the stabilizer group is generally non-abelian. We show that the idea of operator matching continues to hold for such codes and is sufficient for generating all their XP symmetries provided the resulting code is XP. We provide an efficient classical algorithm for tracking these symmetries under tensor contracti… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.19538v1-abstract-full').style.display = 'inline'; document.getElementById('2310.19538v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.19538v1-abstract-full" style="display: none;"> We apply the recent graphical framework of ''quantum lego'' to XP stabilizer codes where the stabilizer group is generally non-abelian. We show that the idea of operator matching continues to hold for such codes and is sufficient for generating all their XP symmetries provided the resulting code is XP. We provide an efficient classical algorithm for tracking these symmetries under tensor contraction or conjoining. This constitutes a partial extension of the algorithm implied by Gottesman-Knill theorem beyond Pauli stabilizer states and Clifford operations. Because conjoining transformations generate quantum operations that are universal, the XP symmetries obtained from these algorithms do not uniquely identify the resulting tensors in general. Using this extended framework, we provide a novel XP stabilizer code with higher distance and a $[[8,1,2]]$ code with fault-tolerant $T$ gate. For XP regular codes, we also construct a tensor-network-based the maximum likelihood decoder for any i.i.d. single qubit error channel. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.19538v1-abstract-full').style.display = 'none'; document.getElementById('2310.19538v1-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 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages, 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/2310.12389">arXiv:2310.12389</a> <span> [<a href="https://arxiv.org/pdf/2310.12389">pdf</a>, <a href="https://arxiv.org/format/2310.12389">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Networking and Internet Architecture">cs.NI</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 Computing for MIMO Beam Selection Problem: Model and Optical Experimental Solution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Huang%2C+Y">Yuhong Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+W">Wenxin Li</a>, <a href="/search/quant-ph?searchtype=author&query=Pan%2C+C">Chengkang Pan</a>, <a href="/search/quant-ph?searchtype=author&query=Hou%2C+S">Shuai Hou</a>, <a href="/search/quant-ph?searchtype=author&query=Lu%2C+X">Xian Lu</a>, <a href="/search/quant-ph?searchtype=author&query=Cui%2C+C">Chunfeng Cui</a>, <a href="/search/quant-ph?searchtype=author&query=Wen%2C+J">Jingwei Wen</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+J">Jiaqi Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chongyu Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Ma%2C+Y">Yin Ma</a>, <a href="/search/quant-ph?searchtype=author&query=Wei%2C+H">Hai Wei</a>, <a href="/search/quant-ph?searchtype=author&query=Wen%2C+K">Kai Wen</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="2310.12389v2-abstract-short" style="display: inline;"> Massive multiple-input multiple-output (MIMO) has gained widespread popularity in recent years due to its ability to increase data rates, improve signal quality, and provide better coverage in challenging environments. In this paper, we investigate the MIMO beam selection (MBS) problem, which is proven to be NP-hard and computationally intractable. To deal with this problem, quantum computing that… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.12389v2-abstract-full').style.display = 'inline'; document.getElementById('2310.12389v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.12389v2-abstract-full" style="display: none;"> Massive multiple-input multiple-output (MIMO) has gained widespread popularity in recent years due to its ability to increase data rates, improve signal quality, and provide better coverage in challenging environments. In this paper, we investigate the MIMO beam selection (MBS) problem, which is proven to be NP-hard and computationally intractable. To deal with this problem, quantum computing that can provide faster and more efficient solutions to large-scale combinatorial optimization is considered. MBS is formulated in a quadratic unbounded binary optimization form and solved with Coherent Ising Machine (CIM) physical machine. We compare the performance of our solution with two classic heuristics, simulated annealing and Tabu search. The results demonstrate an average performance improvement by a factor of 261.23 and 20.6, respectively, which shows that CIM-based solution performs significantly better in terms of selecting the optimal subset of beams. This work shows great promise for practical 5G operation and promotes the application of quantum computing in solving computationally hard problems in communication. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.12389v2-abstract-full').style.display = 'none'; document.getElementById('2310.12389v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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 Globecom 2023</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.05152">arXiv:2308.05152</a> <span> [<a href="https://arxiv.org/pdf/2308.05152">pdf</a>, <a href="https://arxiv.org/format/2308.05152">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="Strongly Correlated Electrons">cond-mat.str-el</span> </div> </div> <p class="title is-5 mathjax"> Quantum Lego Expansion Pack: Enumerators from Tensor Networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Gullans%2C+M+J">Michael J. Gullans</a>, <a href="/search/quant-ph?searchtype=author&query=Lackey%2C+B">Brad Lackey</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+Z">Zitao 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="2308.05152v2-abstract-short" style="display: inline;"> We provide the first tensor network method for computing quantum weight enumerator polynomials in the most general form. If a quantum code has a known tensor network construction of its encoding map, our method is far more efficient, and in some cases exponentially faster than the existing approach. As a corollary, it produces decoders and an algorithm that computes the code distance. For non-(Pau… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.05152v2-abstract-full').style.display = 'inline'; document.getElementById('2308.05152v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.05152v2-abstract-full" style="display: none;"> We provide the first tensor network method for computing quantum weight enumerator polynomials in the most general form. If a quantum code has a known tensor network construction of its encoding map, our method is far more efficient, and in some cases exponentially faster than the existing approach. As a corollary, it produces decoders and an algorithm that computes the code distance. For non-(Pauli)-stabilizer codes, this constitutes the current best algorithm for computing the code distance. For degenerate stabilizer codes, it can be substantially faster compared to the current methods. We also introduce novel weight enumerators and their applications. In particular, we show that these enumerators can be used to compute logical error rates exactly and thus construct (optimal) decoders for any i.i.d. single qubit or qudit error channels. The enumerators also provide a more efficient method for computing non-stabilizerness in quantum many-body states. As the power for these speedups rely on a Quantum Lego decomposition of quantum codes, we further provide systematic methods for decomposing quantum codes and graph states into a modular construction for which our technique applies. As a proof of principle, we perform exact analyses of the deformed surface codes, the holographic pentagon code, and the 2d Bacon-Shor code under (biased) Pauli noise and limited instances of coherent error at sizes that are inaccessible by brute force. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.05152v2-abstract-full').style.display = 'none'; document.getElementById('2308.05152v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 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">46 pages, 25 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/2307.00766">arXiv:2307.00766</a> <span> [<a href="https://arxiv.org/pdf/2307.00766">pdf</a>, <a href="https://arxiv.org/format/2307.00766">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.6.013205">10.1103/PhysRevResearch.6.013205 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Accelerated variational quantum eigensolver with joint Bell measurement </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Yano%2C+H">Hiroshi Yano</a>, <a href="/search/quant-ph?searchtype=author&query=Nakagawa%2C+Y+O">Yuya O. Nakagawa</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="2307.00766v3-abstract-short" style="display: inline;"> The variational quantum eigensolver (VQE) stands as a prominent quantum-classical hybrid algorithm for near-term quantum computers to obtain the ground states of molecular Hamiltonians in quantum chemistry. However, due to the non-commutativity of the Pauli operators in the Hamiltonian, the number of measurements required on quantum computers increases significantly as the system size grows, which… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.00766v3-abstract-full').style.display = 'inline'; document.getElementById('2307.00766v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2307.00766v3-abstract-full" style="display: none;"> The variational quantum eigensolver (VQE) stands as a prominent quantum-classical hybrid algorithm for near-term quantum computers to obtain the ground states of molecular Hamiltonians in quantum chemistry. However, due to the non-commutativity of the Pauli operators in the Hamiltonian, the number of measurements required on quantum computers increases significantly as the system size grows, which may hinder practical applications of VQE. In this work, we present a protocol termed joint Bell measurement VQE (JBM-VQE) to reduce the number of measurements and speed up the VQE algorithm. Our method employs joint Bell measurements, enabling the simultaneous measurement of the absolute values of all expectation values of Pauli operators present in the Hamiltonian. In the course of the optimization, JBM-VQE estimates the absolute values of the expectation values of the Pauli operators for each iteration by the joint Bell measurement, while the signs of them are measured less frequently by the conventional method to measure the expectation values. Our approach is based on the empirical observation that the signs do not often change during optimization. We illustrate the speed-up of JBM-VQE compared to conventional VQE by numerical simulations for finding the ground states of molecular Hamiltonians of small molecules, and the speed-up of JBM-VQE at the early stage of the optimization becomes increasingly pronounced in larger systems. Our approach based on the joint Bell measurement is not limited to VQE and can be utilized in various quantum algorithms whose cost functions are expectation values of many Pauli operators. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.00766v3-abstract-full').style.display = 'none'; document.getElementById('2307.00766v3-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 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 3 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">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 6, 013205 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.17230">arXiv:2306.17230</a> <span> [<a href="https://arxiv.org/pdf/2306.17230">pdf</a>, <a href="https://arxiv.org/format/2306.17230">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="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Superselection Rules, Quantum Error Correction, and Quantum Chromodynamics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Bao%2C+N">Ning Bao</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Chatwin-Davies%2C+A">Aidan Chatwin-Davies</a>, <a href="/search/quant-ph?searchtype=author&query=Cheng%2C+G">Gong Cheng</a>, <a href="/search/quant-ph?searchtype=author&query=Zhu%2C+G">Guanyu Zhu</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="2306.17230v1-abstract-short" style="display: inline;"> We investigate the relationship between superselection rules and quantum error correcting codes. We demonstrate that the existence of a superselection rule implies the Knill-Laflamme condition in quantum error correction. As an example, we examine quantum chromodynamics through the lens of quantum error correction, where the proton and neutron states in the model are explored as different supersel… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.17230v1-abstract-full').style.display = 'inline'; document.getElementById('2306.17230v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.17230v1-abstract-full" style="display: none;"> We investigate the relationship between superselection rules and quantum error correcting codes. We demonstrate that the existence of a superselection rule implies the Knill-Laflamme condition in quantum error correction. As an example, we examine quantum chromodynamics through the lens of quantum error correction, where the proton and neutron states in the model are explored as different superselection sectors that protect logical information. Finally we comment on topological quantum error correcting codes and supersymmetric quantum field theory within this framework. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.17230v1-abstract-full').style.display = 'none'; document.getElementById('2306.17230v1-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 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">27 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/2306.14996">arXiv:2306.14996</a> <span> [<a href="https://arxiv.org/pdf/2306.14996">pdf</a>, <a href="https://arxiv.org/format/2306.14996">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</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"> Non-trivial Area Operators Require Non-local Magic </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</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="2306.14996v2-abstract-short" style="display: inline;"> We show that no stabilizer codes over any local dimension can support a non-trivial area operator for any bipartition of the physical degrees of freedom even if certain code subalgebras contain non-trivial centers. This conclusion also extends to more general quantum codes whose logical operators satisfy certain factorization properties, including any complementary code that encodes qubits and sup… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.14996v2-abstract-full').style.display = 'inline'; document.getElementById('2306.14996v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.14996v2-abstract-full" style="display: none;"> We show that no stabilizer codes over any local dimension can support a non-trivial area operator for any bipartition of the physical degrees of freedom even if certain code subalgebras contain non-trivial centers. This conclusion also extends to more general quantum codes whose logical operators satisfy certain factorization properties, including any complementary code that encodes qubits and supports transversal logical gates that form a nice unitary basis. These results support the observation that some desirable conditions for fault tolerance are in tension with emergent gravity and suggest that non-local "magic" would play an important role in reproducing features of gravitational back-reaction and the quantum extremal surface formula. We comment on conditions needed to circumvent the no-go result and examine some simple instances of non-stabilizer codes that do have non-trivial area operators. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.14996v2-abstract-full').style.display = 'none'; document.getElementById('2306.14996v2-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 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Updated version to match journal submission. Fixed typos, reorganized writing, changed title</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.06378">arXiv:2305.06378</a> <span> [<a href="https://arxiv.org/pdf/2305.06378">pdf</a>, <a href="https://arxiv.org/format/2305.06378">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> </div> </div> <p class="title is-5 mathjax"> Discovery of Optimal Quantum Error Correcting Codes via Reinforcement Learning </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Su%2C+V+P">Vincent Paul Su</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Hu%2C+H">Hong-Ye Hu</a>, <a href="/search/quant-ph?searchtype=author&query=Yanay%2C+Y">Yariv Yanay</a>, <a href="/search/quant-ph?searchtype=author&query=Tahan%2C+C">Charles Tahan</a>, <a href="/search/quant-ph?searchtype=author&query=Swingle%2C+B">Brian Swingle</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="2305.06378v2-abstract-short" style="display: inline;"> The recently introduced Quantum Lego framework provides a powerful method for generating complex quantum error correcting codes (QECCs) out of simple ones. We gamify this process and unlock a new avenue for code design and discovery using reinforcement learning (RL). One benefit of RL is that we can specify \textit{arbitrary} properties of the code to be optimized. We train on two such properties,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.06378v2-abstract-full').style.display = 'inline'; document.getElementById('2305.06378v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.06378v2-abstract-full" style="display: none;"> The recently introduced Quantum Lego framework provides a powerful method for generating complex quantum error correcting codes (QECCs) out of simple ones. We gamify this process and unlock a new avenue for code design and discovery using reinforcement learning (RL). One benefit of RL is that we can specify \textit{arbitrary} properties of the code to be optimized. We train on two such properties, maximizing the code distance, and minimizing the probability of logical error under biased Pauli noise. For the first, we show that the trained agent identifies ways to increase code distance beyond naive concatenation, saturating the linear programming bound for CSS codes on 13 qubits. With a learning objective to minimize the logical error probability under biased Pauli noise, we find the best known CSS code at this task for $\lesssim 20$ qubits. Compared to other (locally deformed) CSS codes, including Surface, XZZX, and 2D Color codes, our $[[17,1,3]]$ code construction actually has \textit{lower} adversarial distance, yet better protects the logical information, highlighting the importance of QECC desiderata. Lastly, we comment on how this RL framework can be used in conjunction with physical quantum devices to tailor a code without explicit characterization of the noise model. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.06378v2-abstract-full').style.display = 'none'; document.getElementById('2305.06378v2-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 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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 + appendices; v2 figure updated and note added</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.02673">arXiv:2304.02673</a> <span> [<a href="https://arxiv.org/pdf/2304.02673">pdf</a>, <a href="https://arxiv.org/format/2304.02673">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</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"> Overlapping qubits from non-isometric maps and de Sitter tensor networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Chemissany%2C+W">Wissam Chemissany</a>, <a href="/search/quant-ph?searchtype=author&query=Jahn%2C+A">Alexander Jahn</a>, <a href="/search/quant-ph?searchtype=author&query=Zimbor%C3%A1s%2C+Z">Zolt谩n Zimbor谩s</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="2304.02673v3-abstract-short" style="display: inline;"> We construct approximately local observables, or "overlapping qubits", using non-isometric maps and show that processes in local effective theories can be spoofed with a quantum system with fewer degrees of freedom, similar to our expectation in holography. Furthermore, the spoofed system naturally deviates from an actual local theory in ways that can be identified with features in quantum gravity… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.02673v3-abstract-full').style.display = 'inline'; document.getElementById('2304.02673v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.02673v3-abstract-full" style="display: none;"> We construct approximately local observables, or "overlapping qubits", using non-isometric maps and show that processes in local effective theories can be spoofed with a quantum system with fewer degrees of freedom, similar to our expectation in holography. Furthermore, the spoofed system naturally deviates from an actual local theory in ways that can be identified with features in quantum gravity. For a concrete example, we construct two MERA toy models of de Sitter space-time and explain how the exponential expansion in global de Sitter can be spoofed with many fewer quantum degrees of freedom and that local physics may be approximately preserved for an exceedingly long time before breaking down. We highlight how approximate overlapping qubits are conceptually connected to Hilbert space dimension verification, degree-of-freedom counting in black holes and holography, and approximate locality in quantum gravity. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.02673v3-abstract-full').style.display = 'none'; document.getElementById('2304.02673v3-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 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 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">17 pages, 15 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/2211.08448">arXiv:2211.08448</a> <span> [<a href="https://arxiv.org/pdf/2211.08448">pdf</a>, <a href="https://arxiv.org/ps/2211.08448">ps</a>, <a href="https://arxiv.org/format/2211.08448">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="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Large $N$ Matrix Quantum Mechanics as a Quantum Memory </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Cheng%2C+G">Gong Cheng</a>, <a href="/search/quant-ph?searchtype=author&query=Swingle%2C+B">Brian Swingle</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="2211.08448v1-abstract-short" style="display: inline;"> In this paper, we explore the possibility of building a quantum memory that is robust to thermal noise using large $N$ matrix quantum mechanics models. First, we investigate the gauged $SU(N)$ matrix harmonic oscillator and different ways to encode quantum information in it. By calculating the mutual information between the system and a reference which purifies the encoded information, we identify… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.08448v1-abstract-full').style.display = 'inline'; document.getElementById('2211.08448v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.08448v1-abstract-full" style="display: none;"> In this paper, we explore the possibility of building a quantum memory that is robust to thermal noise using large $N$ matrix quantum mechanics models. First, we investigate the gauged $SU(N)$ matrix harmonic oscillator and different ways to encode quantum information in it. By calculating the mutual information between the system and a reference which purifies the encoded information, we identify a transition temperature, $T_c$, below which the encoded quantum information is protected from thermal noise for a memory time scaling as $N^2$. Conversely, for temperatures higher than $T_c$, the information is quickly destroyed by thermal noise. Second, we relax the requirement of gauge invariance and study a matrix harmonic oscillator model with only global symmetry. Finally, we further relax even the symmetry requirement and propose a model that consists of a large number $N^2$ of qubits, with interactions derived from an approximate $SU(N)$ symmetry. In both ungauged models, we find that the effects of gauging can be mimicked using an energy penalty to give a similar result for the memory time. The final qubit model also has the potential to be realized in the laboratory. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.08448v1-abstract-full').style.display = 'none'; document.getElementById('2211.08448v1-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 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">45 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/2211.02756">arXiv:2211.02756</a> <span> [<a href="https://arxiv.org/pdf/2211.02756">pdf</a>, <a href="https://arxiv.org/format/2211.02756">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"> Quantum weight enumerators and tensor networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Lackey%2C+B">Brad Lackey</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="2211.02756v2-abstract-short" style="display: inline;"> We examine the use of weight enumerators for analyzing tensor network constructions, and specifically the quantum lego framework recently introduced. We extend the notion of quantum weight enumerators to so-called tensor enumerators, and prove that the trace operation on tensor networks is compatible with a trace operation on tensor enumerators. This allows us to compute quantum weight enumerators… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.02756v2-abstract-full').style.display = 'inline'; document.getElementById('2211.02756v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.02756v2-abstract-full" style="display: none;"> We examine the use of weight enumerators for analyzing tensor network constructions, and specifically the quantum lego framework recently introduced. We extend the notion of quantum weight enumerators to so-called tensor enumerators, and prove that the trace operation on tensor networks is compatible with a trace operation on tensor enumerators. This allows us to compute quantum weight enumerators of larger codes such as the ones constructed through tensor network methods more efficiently. We also provide a general framework for quantum MacWilliams identities that includes tensor enumerators as a special case. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.02756v2-abstract-full').style.display = 'none'; document.getElementById('2211.02756v2-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, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 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">15 pages, 3 figures. Sets up the tensor enumerator formalism</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.02822">arXiv:2210.02822</a> <span> [<a href="https://arxiv.org/pdf/2210.02822">pdf</a>, <a href="https://arxiv.org/format/2210.02822">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.5.023147">10.1103/PhysRevResearch.5.023147 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Solution of SAT Problems with the Adaptive-Bias Quantum Approximate Optimization Algorithm </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Yu%2C+Y">Yunlong Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+X">Xiang-Bin Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Shannon%2C+N">Nic Shannon</a>, <a href="/search/quant-ph?searchtype=author&query=Joynt%2C+R">Robert Joynt</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="2210.02822v3-abstract-short" style="display: inline;"> The quantum approximate optimization algorithm (QAOA) is a promising method for solving certain classical combinatorial optimization problems on near-term quantum devices. When employing the QAOA to 3-SAT and Max-3-SAT problems, the quantum cost exhibits an easy-hard-easy or easy-hard pattern respectively as the clause density is changed. The quantum resources needed in the hard-region problems ar… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.02822v3-abstract-full').style.display = 'inline'; document.getElementById('2210.02822v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.02822v3-abstract-full" style="display: none;"> The quantum approximate optimization algorithm (QAOA) is a promising method for solving certain classical combinatorial optimization problems on near-term quantum devices. When employing the QAOA to 3-SAT and Max-3-SAT problems, the quantum cost exhibits an easy-hard-easy or easy-hard pattern respectively as the clause density is changed. The quantum resources needed in the hard-region problems are out of reach for current NISQ devices. We show by numerical simulations with up to 14 variables and analytical arguments that the adaptive-bias QAOA (ab-QAOA) greatly improves performance in the hard region of the 3-SAT problems and hard region of the Max-3-SAT problems. For similar accuracy, on average, ab-QAOA needs 3 levels for 10-variable 3-SAT problems as compared to 22 for QAOA. For 10-variable Max-3-SAT problems, the numbers are 7 levels and 62 levels. The improvement comes from a more targeted and more limited generation of entanglement during the evolution. We demonstrate that classical optimization is not strictly necessary in the ab-QAOA since local fields are used to guide the evolution. This leads us to propose an optimization-free ab-QAOA that can solve the hard-region 3-SAT and Max-3-SAT problems effectively with significantly fewer quantum gates as compared to the original ab-QAOA. Our work paves the way for realizing quantum advantages for optimization problems on NISQ devices. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.02822v3-abstract-full').style.display = 'none'; document.getElementById('2210.02822v3-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 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 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">18 pages, 15 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 5, 023147(2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.12903">arXiv:2209.12903</a> <span> [<a href="https://arxiv.org/pdf/2209.12903">pdf</a>, <a href="https://arxiv.org/format/2209.12903">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</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/10.1007/JHEP12(2022)124">10.1007/JHEP12(2022)124 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Holographic measurement and bulk teleportation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Antonini%2C+S">Stefano Antonini</a>, <a href="/search/quant-ph?searchtype=author&query=Bentsen%2C+G">Gregory Bentsen</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Harper%2C+J">Jonathan Harper</a>, <a href="/search/quant-ph?searchtype=author&query=Jian%2C+S">Shao-Kai Jian</a>, <a href="/search/quant-ph?searchtype=author&query=Swingle%2C+B">Brian Swingle</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="2209.12903v1-abstract-short" style="display: inline;"> Holography has taught us that spacetime is emergent and its properties depend on the entanglement structure of the dual theory. In this paper, we describe how changes in the entanglement due to a local projective measurement (LPM) on a subregion $A$ of the boundary theory modify the bulk dual spacetime. We find that LPMs destroy portions of the bulk geometry, yielding post-measurement bulk spaceti… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.12903v1-abstract-full').style.display = 'inline'; document.getElementById('2209.12903v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.12903v1-abstract-full" style="display: none;"> Holography has taught us that spacetime is emergent and its properties depend on the entanglement structure of the dual theory. In this paper, we describe how changes in the entanglement due to a local projective measurement (LPM) on a subregion $A$ of the boundary theory modify the bulk dual spacetime. We find that LPMs destroy portions of the bulk geometry, yielding post-measurement bulk spacetimes dual to the complementary unmeasured region $A^c$ that are cut off by end-of-the-world branes. Using a bulk calculation in $AdS_3$ and tensor network models of holography, we show that the portions of the bulk geometry that are preserved after the measurement depend on the size of $A$ and the state we project onto. The post-measurement bulk dual to $A^c$ includes regions that were originally part of the entanglement wedge of $A$ prior to measurement. This suggests that LPMs performed on a boundary subregion $A$ teleport part of the bulk information originally encoded in $A$ into the complementary region $A^c$. In semiclassical holography an arbitrary amount of bulk information can be teleported in this way, while in tensor network models the teleported information is upper-bounded by the amount of entanglement shared between $A$ and $A^c$ due to finite-$N$ effects. When $A$ is the union of two disjoint subregions, the measurement triggers an entangled/disentangled phase transition between the remaining two unmeasured subregions, corresponding to a connected/disconnected phase transition in the bulk description. Our results shed new light on the effects of measurement on the entanglement structure of holographic theories and give insight on how bulk information can be manipulated from the boundary theory. They could also be extended to more general quantum systems and tested experimentally, and represent a first step towards a holographic description of measurement-induced phase transitions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.12903v1-abstract-full').style.display = 'none'; document.getElementById('2209.12903v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">60 pages + appendices, 27 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/2209.10934">arXiv:2209.10934</a> <span> [<a href="https://arxiv.org/pdf/2209.10934">pdf</a>, <a href="https://arxiv.org/format/2209.10934">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.6.013249">10.1103/PhysRevResearch.6.013249 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Detecting Entanglement by Pure Bosonic Extension </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zhu%2C+X">Xuanran Zhu</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+C">Chao Zhang</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=Poon%2C+Y+T">Yiu Tung Poon</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="2209.10934v3-abstract-short" style="display: inline;"> In the realm of quantum information theory, the detection and quantification of quantum entanglement stand as paramount tasks. The relative entropy of entanglement (REE) serves as a prominent measure of entanglement, with extensive applications spanning numerous related fields. The positive partial transpose (PPT) criterion, while providing an efficient method for the computation of REE, unfortuna… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.10934v3-abstract-full').style.display = 'inline'; document.getElementById('2209.10934v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.10934v3-abstract-full" style="display: none;"> In the realm of quantum information theory, the detection and quantification of quantum entanglement stand as paramount tasks. The relative entropy of entanglement (REE) serves as a prominent measure of entanglement, with extensive applications spanning numerous related fields. The positive partial transpose (PPT) criterion, while providing an efficient method for the computation of REE, unfortunately, falls short when dealing with bound entanglement. In this study, we propose a method termed "pure bosonic extension" to enhance the practicability of $k$-bosonic extensions, which approximates the set of separable states from the "outside", through a hierarchical structure. It enables efficient characterization of the set of $k$-bosonic extendible states, facilitating the derivation of accurate lower bounds for REE. Compared to the Semi-Definite Programming (SDP) approach, such as the symmetric/bosonic extension function in QETLAB, our algorithm supports much larger dimensions and higher values of extension $k$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.10934v3-abstract-full').style.display = 'none'; document.getElementById('2209.10934v3-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 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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, 8 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/2209.03202">arXiv:2209.03202</a> <span> [<a href="https://arxiv.org/pdf/2209.03202">pdf</a>, <a href="https://arxiv.org/format/2209.03202">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="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Superconductivity">cond-mat.supr-con</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41524-023-01045-0">10.1038/s41524-023-01045-0 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ab initio Quantum Simulation of Strongly Correlated Materials with Quantum Embedding </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Changsu Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Sun%2C+J">Jinzhao Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Yuan%2C+X">Xiao Yuan</a>, <a href="/search/quant-ph?searchtype=author&query=Hu%2C+H">Han-Shi Hu</a>, <a href="/search/quant-ph?searchtype=author&query=Pham%2C+H+Q">Hung Q. Pham</a>, <a href="/search/quant-ph?searchtype=author&query=Lv%2C+D">Dingshun Lv</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="2209.03202v2-abstract-short" style="display: inline;"> Quantum computing has shown great potential in various quantum chemical applications such as drug discovery, material design, and catalyst optimization. Although significant progress has been made in quantum simulation of simple molecules, ab initio simulation of solid-state materials on quantum computers is still in its early stage, mostly owing to the fact that the system size quickly becomes pr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.03202v2-abstract-full').style.display = 'inline'; document.getElementById('2209.03202v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.03202v2-abstract-full" style="display: none;"> Quantum computing has shown great potential in various quantum chemical applications such as drug discovery, material design, and catalyst optimization. Although significant progress has been made in quantum simulation of simple molecules, ab initio simulation of solid-state materials on quantum computers is still in its early stage, mostly owing to the fact that the system size quickly becomes prohibitively large when approaching the thermodynamic limit. In this work, we introduce an orbital-based multi-fragment approach on top of the periodic density matrix embedding theory, resulting in a significantly smaller problem size for the current near-term quantum computer. We demonstrate the accuracy and efficiency of our method compared with the conventional methodologies and experiments on solid-state systems with complex electronic structures. These include spin polarized states of a hydrogen chain (1D-H), the equation of states of a boron nitride layer (h-BN) as well as the magnetic ordering in nickel oxide (NiO), a prototypical strongly correlated solid. Our results suggest that quantum embedding combined with a chemically intuitive fragmentation can greatly advance quantum simulation of realistic materials, thereby paving the way for solving important yet classically hard industrial problems on near-term quantum devices. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.03202v2-abstract-full').style.display = 'none'; document.getElementById('2209.03202v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">23 pages, 7 figures, and 3 tables</span> </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/2204.03560">arXiv:2204.03560</a> <span> [<a href="https://arxiv.org/pdf/2204.03560">pdf</a>, <a href="https://arxiv.org/format/2204.03560">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-2022-10-06-828">10.22331/q-2022-10-06-828 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum variational learning for quantum error-correcting codes </p> <p class="authors"> <span class="search-hit">Authors:</span> <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=Wu%2C+Z">Zipeng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Grassl%2C+M">Markus Grassl</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="2204.03560v3-abstract-short" style="display: inline;"> Quantum error correction is believed to be a necessity for large-scale fault-tolerant quantum computation. In the past two decades, various constructions of quantum error-correcting codes (QECCs) have been developed, leading to many good code families. However, the majority of these codes are not suitable for near-term quantum devices. Here we present VarQEC, a noise-resilient variational quantum… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2204.03560v3-abstract-full').style.display = 'inline'; document.getElementById('2204.03560v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2204.03560v3-abstract-full" style="display: none;"> Quantum error correction is believed to be a necessity for large-scale fault-tolerant quantum computation. In the past two decades, various constructions of quantum error-correcting codes (QECCs) have been developed, leading to many good code families. However, the majority of these codes are not suitable for near-term quantum devices. Here we present VarQEC, a noise-resilient variational quantum algorithm to search for quantum codes with a hardware-efficient encoding circuit. The cost functions are inspired by the most general and fundamental requirements of a QECC, the Knill-Laflamme conditions. Given the target noise channel (or the target code parameters) and the hardware connectivity graph, we optimize a shallow variational quantum circuit to prepare the basis states of an eligible code. In principle, VarQEC can find quantum codes for any error model, whether additive or non-additive, degenerate or non-degenerate, pure or impure. We have verified its effectiveness by (re)discovering some symmetric and asymmetric codes, e.g., $((n,2^{n-6},3))_2$ for $n$ from 7 to 14. We also found new $((6,2,3))_2$ and $((7,2,3))_2$ codes that are not equivalent to any stabilizer code, and extensive numerical evidence with VarQEC suggests that a $((7,3,3))_2$ code does not exist. Furthermore, we found many new channel-adaptive codes for error models involving nearest-neighbor correlated errors. Our work sheds new light on the understanding of QECC in general, which may also help to enhance near-term device performance with channel-adaptive error-correcting codes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2204.03560v3-abstract-full').style.display = 'none'; document.getElementById('2204.03560v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">34 pages, 14 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum 6, 828 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2203.10200">arXiv:2203.10200</a> <span> [<a href="https://arxiv.org/pdf/2203.10200">pdf</a>, <a href="https://arxiv.org/format/2203.10200">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="Disordered Systems and Neural Networks">cond-mat.dis-nn</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Machine Learning">cs.LG</span> </div> </div> <p class="title is-5 mathjax"> Emulating Quantum Dynamics with Neural Networks via Knowledge Distillation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Yao%2C+Y">Yu Yao</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chao Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Haas%2C+S">Stephan Haas</a>, <a href="/search/quant-ph?searchtype=author&query=Agarwal%2C+M">Mahak Agarwal</a>, <a href="/search/quant-ph?searchtype=author&query=Khanna%2C+D">Divyam Khanna</a>, <a href="/search/quant-ph?searchtype=author&query=Abram%2C+M">Marcin Abram</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="2203.10200v1-abstract-short" style="display: inline;"> High-fidelity quantum dynamics emulators can be used to predict the time evolution of complex physical systems. Here, we introduce an efficient training framework for constructing machine learning-based emulators. Our approach is based on the idea of knowledge distillation and uses elements of curriculum learning. It works by constructing a set of simple, but rich-in-physics training examples (a c… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.10200v1-abstract-full').style.display = 'inline'; document.getElementById('2203.10200v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.10200v1-abstract-full" style="display: none;"> High-fidelity quantum dynamics emulators can be used to predict the time evolution of complex physical systems. Here, we introduce an efficient training framework for constructing machine learning-based emulators. Our approach is based on the idea of knowledge distillation and uses elements of curriculum learning. It works by constructing a set of simple, but rich-in-physics training examples (a curriculum). These examples are used by the emulator to learn the general rules describing the time evolution of a quantum system (knowledge distillation). The goal is not only to obtain high-quality predictions, but also to examine the process of how the emulator learns the physics of the underlying problem. This allows us to discover new facts about the physical system, detect symmetries, and measure relative importance of the contributing physical processes. We illustrate this approach by training an artificial neural network to predict the time evolution of quantum wave packages propagating through a potential landscape. We focus on the question of how the emulator learns the rules of quantum dynamics from the curriculum of simple training examples and to which extent it can generalize the acquired knowledge to solve more challenging cases. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.10200v1-abstract-full').style.display = 'none'; document.getElementById('2203.10200v1-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 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">11 pages plus methods plus supplementary information</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">ACM Class:</span> I.2.6; I.4.m; I.5.4; I.6.0 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.04710">arXiv:2202.04710</a> <span> [<a href="https://arxiv.org/pdf/2202.04710">pdf</a>, <a href="https://arxiv.org/format/2202.04710">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Nuclear Theory">nucl-th</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/PhysRevD.106.046009">10.1103/PhysRevD.106.046009 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Deconfinement and Error Thresholds in Holography </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Bao%2C+N">Ning Bao</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhu%2C+G">Guanyu Zhu</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="2202.04710v2-abstract-short" style="display: inline;"> We study the error threshold properties of holographic quantum error-correcting codes. We demonstrate that holographic CFTs admit an algebraic threshold, which is related to the confinement-deconfinement phase transition. We then apply geometric intuition from holography and the Hawking-Page phase transition to motivate the CFT result, and comment on potential extensions to other confining theorie… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.04710v2-abstract-full').style.display = 'inline'; document.getElementById('2202.04710v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.04710v2-abstract-full" style="display: none;"> We study the error threshold properties of holographic quantum error-correcting codes. We demonstrate that holographic CFTs admit an algebraic threshold, which is related to the confinement-deconfinement phase transition. We then apply geometric intuition from holography and the Hawking-Page phase transition to motivate the CFT result, and comment on potential extensions to other confining theories. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.04710v2-abstract-full').style.display = 'none'; document.getElementById('2202.04710v2-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> 17 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">6 pages, 3 figures. Updated to match published version</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2112.00199">arXiv:2112.00199</a> <span> [<a href="https://arxiv.org/pdf/2112.00199">pdf</a>, <a href="https://arxiv.org/format/2112.00199">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</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"> From Quantum Codes to Gravity: A Journey of Gravitizing Quantum Mechanics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</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="2112.00199v1-abstract-short" style="display: inline;"> In this note, I review a recent approach to quantum gravity that "gravitizes" quantum mechanics by emerging geometry and gravity from complex quantum states. Drawing further insights from tensor network toy models in AdS/CFT, I propose that approximate quantum error correction codes, when re-adapted into the aforementioned framework, also has promise in emerging gravity in near-flat geometries. </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.00199v1-abstract-full" style="display: none;"> In this note, I review a recent approach to quantum gravity that "gravitizes" quantum mechanics by emerging geometry and gravity from complex quantum states. Drawing further insights from tensor network toy models in AdS/CFT, I propose that approximate quantum error correction codes, when re-adapted into the aforementioned framework, also has promise in emerging gravity in near-flat geometries. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.00199v1-abstract-full').style.display = 'none'; document.getElementById('2112.00199v1-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 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">Note prepared as a proceeding for TQTG2021</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2109.08158">arXiv:2109.08158</a> <span> [<a href="https://arxiv.org/pdf/2109.08158">pdf</a>, <a href="https://arxiv.org/format/2109.08158">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="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PRXQuantum.3.020332">10.1103/PRXQuantum.3.020332 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum Lego: Building Quantum Error Correction Codes from Tensor Networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Lackey%2C+B">Brad Lackey</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="2109.08158v2-abstract-short" style="display: inline;"> We introduce a flexible and graphically intuitive framework that constructs complex quantum error correction codes from simple codes or states, generalizing code concatenation. More specifically, we represent the complex code constructions as tensor networks built from the tensors of simple codes or states in a modular fashion. Using a set of local moves known as operator pushing, one can derive p… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.08158v2-abstract-full').style.display = 'inline'; document.getElementById('2109.08158v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.08158v2-abstract-full" style="display: none;"> We introduce a flexible and graphically intuitive framework that constructs complex quantum error correction codes from simple codes or states, generalizing code concatenation. More specifically, we represent the complex code constructions as tensor networks built from the tensors of simple codes or states in a modular fashion. Using a set of local moves known as operator pushing, one can derive properties of the more complex codes, such as transversal non-Clifford gates, by tracing the flow of operators in the network. The framework endows a network geometry to any code it builds and is valid for constructing stabilizer codes as well as non-stabilizer codes over qubits and qudits. For a contractible tensor network, the sequence of contractions also constructs a decoding/encoding circuit. To highlight the framework's range of capabilities and to provide a tutorial, we lay out some examples where we glue together simple stabilizer codes to construct non-trivial codes. These examples include the toric code and its variants, a holographic code with transversal non-Clifford operators, a 3d stabilizer code, and other stabilizer codes with interesting properties. Surprisingly, we find that the surface code is equivalent to the 2d Bacon-Shor code after "dualizing" its tensor network encoding map. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.08158v2-abstract-full').style.display = 'none'; document.getElementById('2109.08158v2-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 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">Updated text to match published version: corrected errors in appendix D1, added theorems for stabilizer code tracing and theorems for expressivity of atomic legos</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> PRX Quantum 3, 020332 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2109.08132">arXiv:2109.08132</a> <span> [<a href="https://arxiv.org/pdf/2109.08132">pdf</a>, <a href="https://arxiv.org/format/2109.08132">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/ac969c">10.1088/2058-9565/ac969c <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Mitigating algorithmic errors in quantum optimization through energy extrapolation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+Y">Yunlong Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Wu%2C+Z">Zipeng Wu</a>, <a href="/search/quant-ph?searchtype=author&query=Shannon%2C+N">Nic Shannon</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+B">Bei Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Joynt%2C+R">Robert Joynt</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="2109.08132v5-abstract-short" style="display: inline;"> Quantum optimization algorithms offer a promising route to finding the ground states of target Hamiltonians on near-term quantum devices. None the less, it remains necessary to limit the evolution time and circuit depth as much as possible, since otherwise decoherence will degrade the computation. And even where this is done, there always exists a non-negligible error in estimates of the ground st… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.08132v5-abstract-full').style.display = 'inline'; document.getElementById('2109.08132v5-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.08132v5-abstract-full" style="display: none;"> Quantum optimization algorithms offer a promising route to finding the ground states of target Hamiltonians on near-term quantum devices. None the less, it remains necessary to limit the evolution time and circuit depth as much as possible, since otherwise decoherence will degrade the computation. And even where this is done, there always exists a non-negligible error in estimates of the ground state energy. Here we present a scalable extrapolation approach to mitigating this error, which significantly improves estimates obtained using three of the most popular optimization algorithms: quantum annealing (QA), the variational quantum eigensolver (VQE), and quantum imaginary time evolution (QITE), at fixed evolution time or circuit depth. The approach is based on extrapolating the annealing time to infinity, or the variance of estimates to zero. The method is reasonably robust against noise, and for Hamiltonians which only involve few-body interactions, the additional computational overhead is an increase in the number of measurements by a constant factor. Analytic derivations are provided for the quadratic convergence of estimates of energy as a function of time in QA, and the linear convergence of estimates as a function of variance in all three algorithms. We have verified the validity of these approaches through both numerical simulation and experiments on an IBM quantum computer. This work suggests a promising new way to enhance near-term quantum computing through classical post-processing. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.08132v5-abstract-full').style.display = 'none'; document.getElementById('2109.08132v5-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 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">16 pages, 9 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. 8 015004 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2109.08062">arXiv:2109.08062</a> <span> [<a href="https://arxiv.org/pdf/2109.08062">pdf</a>, <a href="https://arxiv.org/format/2109.08062">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/10.1039/d2sc01492k">10.1039/d2sc01492k <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Toward Practical Quantum Embedding Simulation of Realistic Chemical Systems on Near-term Quantum Computers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Li%2C+W">Weitang Li</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+Z">Zigeng Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Changsu Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+Y">Yifei Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Shuai%2C+Z">Zhigang Shuai</a>, <a href="/search/quant-ph?searchtype=author&query=Sun%2C+X">Xiaoming Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Sun%2C+J">Jinzhao Sun</a>, <a href="/search/quant-ph?searchtype=author&query=Yuan%2C+X">Xiao Yuan</a>, <a href="/search/quant-ph?searchtype=author&query=Lv%2C+D">Dingshun Lv</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="2109.08062v1-abstract-short" style="display: inline;"> Quantum computing has recently exhibited great potentials in predicting chemical properties for various applications in drug discovery, material design, and catalyst optimization. Progress has been made in simulating small molecules, such as LiH and hydrogen chains of up to 12 qubits, by using quantum algorithms such as variational quantum eigensolver (VQE). Yet, originating from limitations of th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.08062v1-abstract-full').style.display = 'inline'; document.getElementById('2109.08062v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.08062v1-abstract-full" style="display: none;"> Quantum computing has recently exhibited great potentials in predicting chemical properties for various applications in drug discovery, material design, and catalyst optimization. Progress has been made in simulating small molecules, such as LiH and hydrogen chains of up to 12 qubits, by using quantum algorithms such as variational quantum eigensolver (VQE). Yet, originating from limitations of the size and the fidelity of near-term quantum hardware, how to accurately simulate large realistic molecules remains a challenge. Here, integrating an adaptive energy sorting strategy and a classical computational method, the density matrix embedding theory, which effectively finds a shallower quantum circuit and reduces the problem size, respectively, we show a means to circumvent the limitations and demonstrate the potential toward solving real chemical problems. We numerically test the method for the hydrogenation reaction of C6H8 and the equilibrium geometry of the C18 molecule, with basis sets up to cc-pVDZ (at most 144 qubits). The simulation results show accuracies comparable to those of advanced quantum chemistry methods such as coupled-cluster or even full configuration interaction, while the number of qubits required is reduced by an order of magnitude (from 144 qubits to 16 qubits for the C18 molecule) compared to conventional VQE. Our work implies the possibility of solving industrial chemical problems on near-term quantum devices. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.08062v1-abstract-full').style.display = 'none'; document.getElementById('2109.08062v1-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 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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, 5 figures, 1 table</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2109.02110">arXiv:2109.02110</a> <span> [<a href="https://arxiv.org/pdf/2109.02110">pdf</a>, <a href="https://arxiv.org/format/2109.02110">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.105.062452">10.1103/PhysRevA.105.062452 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Towards a Larger Molecular Simulation on the Quantum Computer: Up to 28 Qubits Systems Accelerated by Point Group Symmetry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Changsu Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Hu%2C+J">Jiaqi Hu</a>, <a href="/search/quant-ph?searchtype=author&query=Zhang%2C+W">Wengang Zhang</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+X">Xusheng Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Chen%2C+D">Dechin Chen</a>, <a href="/search/quant-ph?searchtype=author&query=Yu%2C+F">Fan Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+J">Jun Li</a>, <a href="/search/quant-ph?searchtype=author&query=Hu%2C+H">Hanshi Hu</a>, <a href="/search/quant-ph?searchtype=author&query=Lv%2C+D">Dingshun Lv</a>, <a href="/search/quant-ph?searchtype=author&query=Yung%2C+M">Man-Hong Yung</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="2109.02110v2-abstract-short" style="display: inline;"> The exact evaluation of the molecular ground state in quantum chemistry requires an exponentially increasing computational cost. Quantum computation is a promising way to overcome the exponential problem using polynomial-time quantum algorithms. A quantum-classical hybrid optimization scheme known as the variational quantum eigensolver(VQE) is preferred for noisy intermediate-scale quantum devices… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.02110v2-abstract-full').style.display = 'inline'; document.getElementById('2109.02110v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.02110v2-abstract-full" style="display: none;"> The exact evaluation of the molecular ground state in quantum chemistry requires an exponentially increasing computational cost. Quantum computation is a promising way to overcome the exponential problem using polynomial-time quantum algorithms. A quantum-classical hybrid optimization scheme known as the variational quantum eigensolver(VQE) is preferred for noisy intermediate-scale quantum devices. However, the circuit depth becomes one of the bottlenecks of its application to large molecules of more than 20 qubits. In this work, we employ the point group symmetry to reduce the number of operators in constructing ansatz so as to achieve a more compact quantum circuit. We illustrate this methodology with a series of molecules ranging from LiH(12 qubits) to C2H4(28 qubits). A significant reduction of up to 82% of the operator numbers is reached on C2H4, which enables the largest molecule ever numerically simulated by VQE-UCC to the best of our knowledge. This also shed light into the further work of this direction to construct even shallower ansatz with enough expressive power and simulate even larger scale system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.02110v2-abstract-full').style.display = 'none'; document.getElementById('2109.02110v2-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> 8 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">12 pages, 9 figures, 2 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2107.03542">arXiv:2107.03542</a> <span> [<a href="https://arxiv.org/pdf/2107.03542">pdf</a>, <a href="https://arxiv.org/format/2107.03542">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-2024-07-22-1421">10.22331/q-2024-07-22-1421 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Learning quantum phases via single-qubit disentanglement </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=An%2C+Z">Zheng An</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+C">Cheng-Qian Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+D+L">D. L. 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="2107.03542v4-abstract-short" style="display: inline;"> Identifying phases of matter presents considerable challenges, particularly within the domain of quantum theory, where the complexity of ground states appears to increase exponentially with system size. Quantum many-body systems exhibit an array of complex entanglement structures spanning distinct phases. Although extensive research has explored the relationship between quantum phase transitions a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.03542v4-abstract-full').style.display = 'inline'; document.getElementById('2107.03542v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.03542v4-abstract-full" style="display: none;"> Identifying phases of matter presents considerable challenges, particularly within the domain of quantum theory, where the complexity of ground states appears to increase exponentially with system size. Quantum many-body systems exhibit an array of complex entanglement structures spanning distinct phases. Although extensive research has explored the relationship between quantum phase transitions and quantum entanglement, establishing a direct, pragmatic connection between them remains a critical challenge. In this work, we present a novel and efficient quantum phase transition classifier, utilizing disentanglement with reinforcement learning-optimized variational quantum circuits. We demonstrate the effectiveness of this method on quantum phase transitions in the transverse field Ising model (TFIM) and the XXZ model. Moreover, we observe the algorithm's ability to learn the Kramers-Wannier duality pertaining to entanglement structures in the TFIM. Our approach not only identifies phase transitions based on the performance of the disentangling circuits but also exhibits impressive scalability, facilitating its application in larger and more complex quantum systems. This study sheds light on the characterization of quantum phases through the entanglement structures inherent in quantum many-body systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.03542v4-abstract-full').style.display = 'none'; document.getElementById('2107.03542v4-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, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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, 21 figures, accepted for publication in Quantum</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum 8, 1421 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.15210">arXiv:2106.15210</a> <span> [<a href="https://arxiv.org/pdf/2106.15210">pdf</a>, <a href="https://arxiv.org/format/2106.15210">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"> Circuit-Depth Reduction of Unitary-Coupled-Cluster Ansatz by Energy Sorting </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Fan%2C+Y">Yi Fan</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Changsu Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Xu%2C+X">Xusheng Xu</a>, <a href="/search/quant-ph?searchtype=author&query=Li%2C+Z">Zhenyu Li</a>, <a href="/search/quant-ph?searchtype=author&query=Lv%2C+D">Dingshun Lv</a>, <a href="/search/quant-ph?searchtype=author&query=Yung%2C+M">Man-Hong Yung</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2106.15210v2-abstract-short" style="display: inline;"> Quantum computation represents a revolutionary approach for solving problems in quantum chemistry. However, due to the limited quantum resources in the current noisy intermediate-scale quantum (NISQ) devices, quantum algorithms for large chemical systems remains a major task. In this work, we demonstrate that the circuit depth of the unitary coupled cluster (UCC) and UCC-based ansatzes in the algo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.15210v2-abstract-full').style.display = 'inline'; document.getElementById('2106.15210v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.15210v2-abstract-full" style="display: none;"> Quantum computation represents a revolutionary approach for solving problems in quantum chemistry. However, due to the limited quantum resources in the current noisy intermediate-scale quantum (NISQ) devices, quantum algorithms for large chemical systems remains a major task. In this work, we demonstrate that the circuit depth of the unitary coupled cluster (UCC) and UCC-based ansatzes in the algorithm of variational quantum eigensolver can be significantly reduced by an energy-sorting strategy. Specifically, subsets of excitation operators are first pre-screened from the operator pool according to its contribution to the total energy. The quantum circuit ansatz is then iteratively constructed until the convergence of the final energy to a typical accuracy. For demonstration, this method has been successfully applied to molecular and periodic systems. Particularly, a reduction of 50\%$\sim$98\% in the number of operators is observed while retaining the accuracy of the origin UCCSD operator pools. This method can be straightforwardly extended to general parametric variational ansatzes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.15210v2-abstract-full').style.display = 'none'; document.getElementById('2106.15210v2-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, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.12591">arXiv:2106.12591</a> <span> [<a href="https://arxiv.org/pdf/2106.12591">pdf</a>, <a href="https://arxiv.org/format/2106.12591">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevA.105.022602">10.1103/PhysRevA.105.022602 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Magic State Distillation from Entangled States </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Bao%2C+N">Ning Bao</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Su%2C+V+P">Vincent Paul Su</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2106.12591v1-abstract-short" style="display: inline;"> Magic can be distributed non-locally in many-body entangled states, such as the low energy states of condensed matter systems. Using the Bravyi-Kitaev magic state distillation protocol, we find that non-local magic is distillable and can improve the distillation outcome. We analyze a few explicit examples and show that spin squeezing can be used to convert non-distillable states into distillable o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.12591v1-abstract-full').style.display = 'inline'; document.getElementById('2106.12591v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.12591v1-abstract-full" style="display: none;"> Magic can be distributed non-locally in many-body entangled states, such as the low energy states of condensed matter systems. Using the Bravyi-Kitaev magic state distillation protocol, we find that non-local magic is distillable and can improve the distillation outcome. We analyze a few explicit examples and show that spin squeezing can be used to convert non-distillable states into distillable ones. Our analysis also suggests that the conventional product input states assumed by magic distillation protocols are extremely atypical among general states with distillable magic. It further justifies the need for studying a diverse range of entangled inputs that yield magic states with high probability. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.12591v1-abstract-full').style.display = 'none'; document.getElementById('2106.12591v1-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 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 9 figures, 2 appendices</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2105.11946">arXiv:2105.11946</a> <span> [<a href="https://arxiv.org/pdf/2105.11946">pdf</a>, <a href="https://arxiv.org/format/2105.11946">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.4.023249">10.1103/PhysRevResearch.4.023249 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum Approximate Optimization Algorithm with Adaptive Bias Fields </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Yu%2C+Y">Yunlong Yu</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Dewey%2C+C">Carter Dewey</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+X">Xiang-Bin Wang</a>, <a href="/search/quant-ph?searchtype=author&query=Shannon%2C+N">Nic Shannon</a>, <a href="/search/quant-ph?searchtype=author&query=Joynt%2C+R">Robert Joynt</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2105.11946v3-abstract-short" style="display: inline;"> The quantum approximate optimization algorithm (QAOA) transforms a simple many-qubit wavefunction into one which encodes a solution to a difficult classical optimization problem. It does this by optimizing the schedule according to which two unitary operators are alternately applied to the qubits. In this paper, the QAOA is modified by updating the operators themselves to include local fields, usi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.11946v3-abstract-full').style.display = 'inline'; document.getElementById('2105.11946v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2105.11946v3-abstract-full" style="display: none;"> The quantum approximate optimization algorithm (QAOA) transforms a simple many-qubit wavefunction into one which encodes a solution to a difficult classical optimization problem. It does this by optimizing the schedule according to which two unitary operators are alternately applied to the qubits. In this paper, the QAOA is modified by updating the operators themselves to include local fields, using information from the measured wavefunction at the end of one iteration step to improve the operators at later steps. It is shown by numerical simulation on MaxCut problems that, for a fixed accuracy, this procedure decreases the runtime of QAOA very substantially. This improvement appears to increase with the problem size. Our method requires essentially the same number of quantum gates per optimization step as the standard QAOA, and no additional measurements. This modified algorithm enhances the prospects for quantum advantage for certain optimization problems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.11946v3-abstract-full').style.display = 'none'; document.getElementById('2105.11946v3-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> 28 June, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages, 13 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 4, 023249 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2105.08696">arXiv:2105.08696</a> <span> [<a href="https://arxiv.org/pdf/2105.08696">pdf</a>, <a href="https://arxiv.org/format/2105.08696">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s42005-022-00837-y">10.1038/s42005-022-00837-y <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum imaginary time evolution steered by reinforcement learning </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=An%2C+Z">Zheng An</a>, <a href="/search/quant-ph?searchtype=author&query=Hou%2C+S">Shi-Yao Hou</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+D+L">D. L. Zhou</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="2105.08696v3-abstract-short" style="display: inline;"> The quantum imaginary time evolution is a powerful algorithm for preparing the ground and thermal states on near-term quantum devices. However, algorithmic errors induced by Trotterization and local approximation severely hinder its performance. Here we propose a deep reinforcement learning-based method to steer the evolution and mitigate these errors. In our scheme, the well-trained agent can fin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.08696v3-abstract-full').style.display = 'inline'; document.getElementById('2105.08696v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2105.08696v3-abstract-full" style="display: none;"> The quantum imaginary time evolution is a powerful algorithm for preparing the ground and thermal states on near-term quantum devices. However, algorithmic errors induced by Trotterization and local approximation severely hinder its performance. Here we propose a deep reinforcement learning-based method to steer the evolution and mitigate these errors. In our scheme, the well-trained agent can find the subtle evolution path where most algorithmic errors cancel out, enhancing the fidelity significantly. We verified the method's validity with the transverse-field Ising model and the Sherrington-Kirkpatrick model. Numerical calculations and experiments on a nuclear magnetic resonance quantum computer illustrate the efficacy. The philosophy of our method, eliminating errors with errors, sheds light on error reduction on near-term quantum devices. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.08696v3-abstract-full').style.display = 'none'; document.getElementById('2105.08696v3-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, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">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> Communications Physics 5, 57 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.08631">arXiv:2103.08631</a> <span> [<a href="https://arxiv.org/pdf/2103.08631">pdf</a>, <a href="https://arxiv.org/format/2103.08631">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="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</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/PhysRevD.105.026018">10.1103/PhysRevD.105.026018 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Hyper-Invariant MERA: Approximate Holographic Error Correction Codes with Power-Law Correlations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Pollack%2C+J">Jason Pollack</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+Y">Yixu 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="2103.08631v1-abstract-short" style="display: inline;"> We consider a class of holographic tensor networks that are efficiently contractible variational ansatze, manifestly (approximate) quantum error correction codes, and can support power-law correlation functions. In the case when the network consists of a single type of tensor that also acts as an erasure correction code, we show that it cannot be both locally contractible and sustain power-law cor… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.08631v1-abstract-full').style.display = 'inline'; document.getElementById('2103.08631v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.08631v1-abstract-full" style="display: none;"> We consider a class of holographic tensor networks that are efficiently contractible variational ansatze, manifestly (approximate) quantum error correction codes, and can support power-law correlation functions. In the case when the network consists of a single type of tensor that also acts as an erasure correction code, we show that it cannot be both locally contractible and sustain power-law correlation functions. Motivated by this no-go theorem, and the desirability of local contractibility for an efficient variational ansatz, we provide guidelines for constructing networks consisting of multiple types of tensors that can support power-law correlation. We also provide an explicit construction of one such network, which approximates the holographic HaPPY pentagon code in the limit where variational parameters are taken to be small. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.08631v1-abstract-full').style.display = 'none'; document.getElementById('2103.08631v1-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">12 pages plus appendices, 19 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review D 2022 (Vol. 105, No. 2) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.06457">arXiv:2103.06457</a> <span> [<a href="https://arxiv.org/pdf/2103.06457">pdf</a>, <a href="https://arxiv.org/format/2103.06457">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"> All-optical neural network quantum state tomography </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Zuo%2C+Y">Ying Zuo</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+N">Ningping Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Lai%2C+X">Xuanying Lai</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+B">Bei Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Du%2C+S">Shengwang Du</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="2103.06457v2-abstract-short" style="display: inline;"> Quantum state tomography (QST) is a crucial ingredient for almost all aspects of experimental quantum information processing. As an analog of the "imaging" technique in the quantum settings, QST is born to be a data science problem, where machine learning techniques, noticeably neural networks, have been applied extensively. In this work, we build an integrated all-optical setup for neural network… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.06457v2-abstract-full').style.display = 'inline'; document.getElementById('2103.06457v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.06457v2-abstract-full" style="display: none;"> Quantum state tomography (QST) is a crucial ingredient for almost all aspects of experimental quantum information processing. As an analog of the "imaging" technique in the quantum settings, QST is born to be a data science problem, where machine learning techniques, noticeably neural networks, have been applied extensively. In this work, we build an integrated all-optical setup for neural network QST, based on an all-optical neural network (AONN). Our AONN is equipped with built-in nonlinear activation function, which is based on electromagnetically induced transparency. Experiment results demonstrate the validity and efficiency of the all-optical setup, indicating that AONN can mitigate the state-preparation-and-measurement error and predict the phase parameter in the quantum state accurately. Given that optical setups are highly desired for future quantum networks, our all-optical setup of integrated AONN-QST may shed light on replenishing the all-optical quantum network with the last brick. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.06457v2-abstract-full').style.display = 'none'; document.getElementById('2103.06457v2-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 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/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/2012.08331">arXiv:2012.08331</a> <span> [<a href="https://arxiv.org/pdf/2012.08331">pdf</a>, <a href="https://arxiv.org/format/2012.08331">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/PhysRevApplied.15.054012">10.1103/PhysRevApplied.15.054012 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Noise-Assisted Quantum Autoencoder </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Wang%2C+X">Xin 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="2012.08331v2-abstract-short" style="display: inline;"> Quantum autoencoder is an efficient variational quantum algorithm for quantum data compression. However, previous quantum autoencoders fail to compress and recover high-rank mixed states. In this work, we discuss the fundamental properties and limitations of the standard quantum autoencoder model in more depth, and provide an information-theoretic solution to its recovering fidelity. Based on this… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.08331v2-abstract-full').style.display = 'inline'; document.getElementById('2012.08331v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2012.08331v2-abstract-full" style="display: none;"> Quantum autoencoder is an efficient variational quantum algorithm for quantum data compression. However, previous quantum autoencoders fail to compress and recover high-rank mixed states. In this work, we discuss the fundamental properties and limitations of the standard quantum autoencoder model in more depth, and provide an information-theoretic solution to its recovering fidelity. Based on this understanding, we present a noise-assisted quantum autoencoder algorithm to go beyond the limitations, our model can achieve high recovering fidelity for general input states. Appropriate noise channels are used to make the input mixedness and output mixedness consistent, the noise setup is determined by measurement results of the trash system. Compared with the original quantum autoencoder model, the measurement information is fully used in our algorithm. In addition to the circuit model, we design a (noise-assisted) adiabatic model of quantum autoencoder that can be implemented on quantum annealers. We verified the validity of our methods through compressing the thermal states of transverse field Ising model and Werner states. For pure state ensemble compression, we also introduce a projected quantum autoencoder algorithm. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.08331v2-abstract-full').style.display = 'none'; document.getElementById('2012.08331v2-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 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 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">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> Phys. Rev. Applied 15, 054012 (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/2010.06339">arXiv:2010.06339</a> <span> [<a href="https://arxiv.org/pdf/2010.06339">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/10.1038/s41598-021-93856-8">10.1038/s41598-021-93856-8 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Phase Analysis on the Error Scaling of Entangled Qubits in a 53-Qubit System </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Huang%2C+W">Wei-Jia Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Chien%2C+W">Wei-Chen Chien</a>, <a href="/search/quant-ph?searchtype=author&query=Cho%2C+C">Chien-Hung Cho</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+C">Che-Chun Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Huang%2C+T">Tsung-Wei Huang</a>, <a href="/search/quant-ph?searchtype=author&query=Tan%2C+S+G">Seng Ghee Tan</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Zeng%2C+B">Bei Zeng</a>, <a href="/search/quant-ph?searchtype=author&query=Chang%2C+C">Ching-Ray Chang</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="2010.06339v2-abstract-short" style="display: inline;"> We have studied carefully the behaviors of entangled qubits on the IBM Rochester with various connectivities and under a "noisy" environment. A phase trajectory analysis based on our measurements of the GHZ-like states is performed. Our results point to an important fact that entangled qubits are "protected" against environmental noise by a scaling property that impacts only the weighting of their… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06339v2-abstract-full').style.display = 'inline'; document.getElementById('2010.06339v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2010.06339v2-abstract-full" style="display: none;"> We have studied carefully the behaviors of entangled qubits on the IBM Rochester with various connectivities and under a "noisy" environment. A phase trajectory analysis based on our measurements of the GHZ-like states is performed. Our results point to an important fact that entangled qubits are "protected" against environmental noise by a scaling property that impacts only the weighting of their amplitudes. The reproducibility of most measurements has been confirmed within a reasonably short gate operation time. But there still are a few combinations of qubits that show significant entanglement evolution in the form of transitions between quantum states. The phase trajectory of an entangled evolution, and the impact of the sudden death of GHZ-like states and the revival of newly excited states are analyzed in details. All observed trajectories of entangled qubits arise under the influences of the newly excited states in a "noisy" intermediate-scale quantum (NISQ) computer. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06339v2-abstract-full').style.display = 'none'; document.getElementById('2010.06339v2-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, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 October, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2020. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2010.05960">arXiv:2010.05960</a> <span> [<a href="https://arxiv.org/pdf/2010.05960">pdf</a>, <a href="https://arxiv.org/format/2010.05960">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</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/10.1007/JHEP05(2021)127">10.1007/JHEP05(2021)127 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Approximate Bacon-Shor Code and Holography </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Lackey%2C+B">Brad Lackey</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="2010.05960v2-abstract-short" style="display: inline;"> We explicitly construct a class of holographic quantum error correction codes with non-trivial centers in the code subalgebra. Specifically, we use the Bacon-Shor codes and perfect tensors to construct a gauge code (or a stabilizer code with gauge-fixing), which we call the holographic hybrid code. This code admits a local log-depth encoding/decoding circuit, and can be represented as a holographi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.05960v2-abstract-full').style.display = 'inline'; document.getElementById('2010.05960v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2010.05960v2-abstract-full" style="display: none;"> We explicitly construct a class of holographic quantum error correction codes with non-trivial centers in the code subalgebra. Specifically, we use the Bacon-Shor codes and perfect tensors to construct a gauge code (or a stabilizer code with gauge-fixing), which we call the holographic hybrid code. This code admits a local log-depth encoding/decoding circuit, and can be represented as a holographic tensor network which satisfies an analog of the Ryu-Takayanagi formula and reproduces features of the sub-region duality. We then construct approximate versions of the holographic hybrid codes by "skewing" the code subspace, where the size of skewing is analogous to the size of the gravitational constant in holography. These approximate hybrid codes are not necessarily stabilizer codes, but they can be expressed as the superposition of holographic tensor networks that are stabilizer codes. For such constructions, different logical states, representing different bulk matter content, can "back-react" on the emergent geometry, resembling a key feature of gravity. The locality of the bulk degrees of freedom becomes subspace-dependent and approximate. Such subspace-dependence is manifest from the point of view of the "entanglement wedge" and bulk operator reconstruction from the boundary. Exact complementary error correction breaks down for certain bipartition of the boundary degrees of freedom; however, a limited, state-dependent form is preserved for particular subspaces. We also construct an example where the connected two-point correlation functions can have a power-law decay. Coupled with known constraints from holography, a weakly back-reacting bulk also forces these skewed tensor network models to the "large $N$ limit" where they are built by concatenating a large $N$ number of copies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.05960v2-abstract-full').style.display = 'none'; document.getElementById('2010.05960v2-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, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 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">Updated to match the published version</span> </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/2007.11212">arXiv:2007.11212</a> <span> [<a href="https://arxiv.org/pdf/2007.11212">pdf</a>, <a href="https://arxiv.org/format/2007.11212">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.3.013092">10.1103/PhysRevResearch.3.013092 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Speedup of the Quantum Adiabatic Algorithm using Delocalization Catalysis </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Xue%2C+J">Jian Xue</a>, <a href="/search/quant-ph?searchtype=author&query=Shannon%2C+N">Nic Shannon</a>, <a href="/search/quant-ph?searchtype=author&query=Joynt%2C+R">Robert Joynt</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="2007.11212v4-abstract-short" style="display: inline;"> We propose a method to speed up the quantum adiabatic algorithm using catalysis by many-body delocalization. This is applied to random-field antiferromagnetic Ising spin models. The algorithm is catalyzed in such a way that the evolution approximates a Heisenberg model in the middle of its course, and the model is in a delocalized phase. We show numerically that we can speed up the standard algori… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.11212v4-abstract-full').style.display = 'inline'; document.getElementById('2007.11212v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.11212v4-abstract-full" style="display: none;"> We propose a method to speed up the quantum adiabatic algorithm using catalysis by many-body delocalization. This is applied to random-field antiferromagnetic Ising spin models. The algorithm is catalyzed in such a way that the evolution approximates a Heisenberg model in the middle of its course, and the model is in a delocalized phase. We show numerically that we can speed up the standard algorithm for finding the ground state of the random-field Ising model using this idea. We also demonstrate that the speedup is due to gap amplification, even though the underlying model is not frustration-free. The crossover to speedup occurs at roughly the value of the interaction which is known to be the critical one for the delocalization transition. We also calculate the participation ratio and entanglement entropy as a function of time: their time dependencies indicate that the system is exploring more states and that they are more entangled than when there is no catalyst. Together, all these pieces of evidence demonstrate that the speedup is related to delocalization. Even though only relatively small systems can be investigated, the evidence suggests that the scaling of the method with system size is favorable. Our method is illustrated by experimental results from a small online IBM quantum computer, showing how to verify the method in future as such machines improve. The cost of the catalytic method compared to the standard algorithm is only a constant factor. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.11212v4-abstract-full').style.display = 'none'; document.getElementById('2007.11212v4-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 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">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. Research 3, 013092 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.05962">arXiv:2007.05962</a> <span> [<a href="https://arxiv.org/pdf/2007.05962">pdf</a>, <a href="https://arxiv.org/format/2007.05962">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/10.1088/1361-648X/abc4cf">10.1088/1361-648X/abc4cf <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Supervised learning in Hamiltonian reconstruction from local measurements on eigenstates </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Hou%2C+S">Shi-Yao Hou</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+N">Ningping Cao</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="2007.05962v2-abstract-short" style="display: inline;"> Reconstructing a system Hamiltonian through measurements on its eigenstates is an important inverse problem in quantum physics. Recently, it was shown that generic many-body local Hamiltonians can be recovered by local measurements without knowing the values of the correlation functions. In this work, we discuss this problem in more depth for different systems and apply the supervised learning met… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.05962v2-abstract-full').style.display = 'inline'; document.getElementById('2007.05962v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.05962v2-abstract-full" style="display: none;"> Reconstructing a system Hamiltonian through measurements on its eigenstates is an important inverse problem in quantum physics. Recently, it was shown that generic many-body local Hamiltonians can be recovered by local measurements without knowing the values of the correlation functions. In this work, we discuss this problem in more depth for different systems and apply the supervised learning method via neural networks to solve it. For low-lying eigenstates, the inverse problem is well-posed, neural networks turn out to be efficient and scalable even with a shallow network and a small data set. For middle-lying eigenstates, the problem is ill-posed, we present a modified method based on transfer learning accordingly. Neural networks can also efficiently generate appropriate initial points for numerical optimization based on the BFGS method. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.05962v2-abstract-full').style.display = 'none'; document.getElementById('2007.05962v2-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 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">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> Journal of Physics: Condensed Matter 33 (6), 064002 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.01303">arXiv:2007.01303</a> <span> [<a href="https://arxiv.org/pdf/2007.01303">pdf</a>, <a href="https://arxiv.org/format/2007.01303">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="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevB.103.075145">10.1103/PhysRevB.103.075145 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Conformal field theories are magical </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=White%2C+C+D">Christopher David White</a>, <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Swingle%2C+B">Brian Swingle</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="2007.01303v1-abstract-short" style="display: inline;"> "Magic" is the degree to which a state cannot be approximated by Clifford gates. We study mana, a measure of magic, in the ground state of the $\mathbb Z_3$ Potts model, and argue that it is a broadly useful diagnostic for many-body physics. In particular we find that the $q = 3$ ground state has large mana at the model's critical point, and that this mana resides in the system's correlations. We… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.01303v1-abstract-full').style.display = 'inline'; document.getElementById('2007.01303v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.01303v1-abstract-full" style="display: none;"> "Magic" is the degree to which a state cannot be approximated by Clifford gates. We study mana, a measure of magic, in the ground state of the $\mathbb Z_3$ Potts model, and argue that it is a broadly useful diagnostic for many-body physics. In particular we find that the $q = 3$ ground state has large mana at the model's critical point, and that this mana resides in the system's correlations. We explain the form of the mana by a simple tensor-counting calculation based on a MERA representation of the state. Because mana is present at all length scales, we conclude that the conformal field theory describing the 3-state Potts model critical point is magical. These results control the difficulty of preparing the Potts ground state on an error-corrected quantum computer, and constrain tensor network models of AdS-CFT. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.01303v1-abstract-full').style.display = 'none'; document.getElementById('2007.01303v1-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, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. B 103, 075145 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.00004">arXiv:2007.00004</a> <span> [<a href="https://arxiv.org/pdf/2007.00004">pdf</a>, <a href="https://arxiv.org/format/2007.00004">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</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/10.1007/JHEP12(2020)033">10.1007/JHEP12(2020)033 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Building Bulk Geometry from the Tensor Radon Transform </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Qi%2C+X">Xiao-Liang Qi</a>, <a href="/search/quant-ph?searchtype=author&query=Swingle%2C+B">Brian Swingle</a>, <a href="/search/quant-ph?searchtype=author&query=Tang%2C+E">Eugene Tang</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="2007.00004v1-abstract-short" style="display: inline;"> Using the tensor Radon transform and related numerical methods, we study how bulk geometries can be explicitly reconstructed from boundary entanglement entropies in the specific case of $\mathrm{AdS}_3/\mathrm{CFT}_2$. We find that, given the boundary entanglement entropies of a $2$d CFT, this framework provides a quantitative measure that detects whether the bulk dual is geometric in the perturba… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.00004v1-abstract-full').style.display = 'inline'; document.getElementById('2007.00004v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.00004v1-abstract-full" style="display: none;"> Using the tensor Radon transform and related numerical methods, we study how bulk geometries can be explicitly reconstructed from boundary entanglement entropies in the specific case of $\mathrm{AdS}_3/\mathrm{CFT}_2$. We find that, given the boundary entanglement entropies of a $2$d CFT, this framework provides a quantitative measure that detects whether the bulk dual is geometric in the perturbative (near AdS) limit. In the case where a well-defined bulk geometry exists, we explicitly reconstruct the unique bulk metric tensor once a gauge choice is made. We then examine the emergent bulk geometries for static and dynamical scenarios in holography and in many-body systems. Apart from the physics results, our work demonstrates that numerical methods are feasible and effective in the study of bulk reconstruction in AdS/CFT. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.00004v1-abstract-full').style.display = 'none'; document.getElementById('2007.00004v1-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 June, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">Animations for dynamical processes are found here: (https://www.youtube.com/playlist?list=PLCjJ3kjqxOfw1aIa5c0X6KSpox1-AjM5b) 23 pages excluding appendices. 21 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/2004.02388">arXiv:2004.02388</a> <span> [<a href="https://arxiv.org/pdf/2004.02388">pdf</a>, <a href="https://arxiv.org/format/2004.02388">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="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Information Theory">cs.IT</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.3.023005">10.1103/PhysRevResearch.3.023005 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Simulating Noisy Quantum Circuits with Matrix Product Density Operators </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cheng%2C+S">Song Cheng</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=Liu%2C+Y">Yongxiang Liu</a>, <a href="/search/quant-ph?searchtype=author&query=Hou%2C+S">Shi-Yao 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="2004.02388v3-abstract-short" style="display: inline;"> Simulating quantum circuits with classical computers requires resources growing exponentially in terms of system size. Real quantum computer with noise, however, may be simulated polynomially with various methods considering different noise models. In this work, we simulate random quantum circuits in 1D with Matrix Product Density Operators (MPDO), for different noise models such as dephasing, dep… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2004.02388v3-abstract-full').style.display = 'inline'; document.getElementById('2004.02388v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2004.02388v3-abstract-full" style="display: none;"> Simulating quantum circuits with classical computers requires resources growing exponentially in terms of system size. Real quantum computer with noise, however, may be simulated polynomially with various methods considering different noise models. In this work, we simulate random quantum circuits in 1D with Matrix Product Density Operators (MPDO), for different noise models such as dephasing, depolarizing, and amplitude damping. We show that the method based on Matrix Product States (MPS) fails to approximate the noisy output quantum states for any of the noise models considered, while the MPDO method approximates them well. Compared with the method of Matrix Product Operators (MPO), the MPDO method reflects a clear physical picture of noise (with inner indices taking care of the noise simulation) and quantum entanglement (with bond indices taking care of two-qubit gate simulation). Consequently, in case of weak system noise, the resource cost of MPDO will be significantly less than that of the MPO due to a relatively small inner dimension needed for the simulation. In case of strong system noise, a relatively small bond dimension may be sufficient to simulate the noisy circuits, indicating a regime that the noise is large enough for an `easy' classical simulation. Moreover, we propose a more effective tensor updates scheme with optimal truncations for both the inner and the bond dimensions, performed after each layer of the circuit, which enjoys a canonical form of the MPDO for improving simulation accuracy. With truncated inner dimension to a maximum value $魏$ and bond dimension to a maximum value $蠂$, the cost of our simulation scales as $\sim ND魏^3蠂^3$, for an $N$-qubit circuit with depth $D$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2004.02388v3-abstract-full').style.display = 'none'; document.getElementById('2004.02388v3-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 November, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 April, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">14 pages, 13 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 3, 023005 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.02335">arXiv:1909.02335</a> <span> [<a href="https://arxiv.org/pdf/1909.02335">pdf</a>, <a href="https://arxiv.org/format/1909.02335">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/abb412">10.1088/2058-9565/abb412 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Upper bounds for relative entropy of entanglement based on active learning </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=Cao%2C+C">Chenfeng Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Zhou%2C+D+L">D. L. Zhou</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="1909.02335v2-abstract-short" style="display: inline;"> Quantifying entanglement for multipartite quantum state is a crucial task in many aspects of quantum information theory. Among all the entanglement measures, relative entropy of entanglement $E_{R}$ is an outstanding quantity due to its clear geometric meaning, easy compatibility with different system sizes, and various applications in many other related quantity calculations. Lower bounds of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.02335v2-abstract-full').style.display = 'inline'; document.getElementById('1909.02335v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.02335v2-abstract-full" style="display: none;"> Quantifying entanglement for multipartite quantum state is a crucial task in many aspects of quantum information theory. Among all the entanglement measures, relative entropy of entanglement $E_{R}$ is an outstanding quantity due to its clear geometric meaning, easy compatibility with different system sizes, and various applications in many other related quantity calculations. Lower bounds of $E_R$ were previously found based on distance to the set of positive partial transpose states. We propose a method to calculate upper bounds of $E_R$ based on active learning, a subfield in machine learning, to generate an approximation of the set of separable states. We apply our method to calculate $E_R$ for composite systems of various sizes, and compare with the previous known lower bounds, obtaining promising results. Our method adds a reliable tool for entanglement measure calculation and deepens our understanding for the structure of separable states. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.02335v2-abstract-full').style.display = 'none'; document.getElementById('1909.02335v2-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 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 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">9 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Quantum Sci. Technol. 5 (2020) 045019 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.11199">arXiv:1905.11199</a> <span> [<a href="https://arxiv.org/pdf/1905.11199">pdf</a>, <a href="https://arxiv.org/format/1905.11199">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</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/10.1142/S0218271819440061">10.1142/S0218271819440061 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> How Low Can Vacuum Energy Go When Your Fields Are Finite-Dimensional? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/quant-ph?searchtype=author&query=Cao%2C+C">ChunJun Cao</a>, <a href="/search/quant-ph?searchtype=author&query=Chatwin-Davies%2C+A">Aidan Chatwin-Davies</a>, <a href="/search/quant-ph?searchtype=author&query=Singh%2C+A">Ashmeet Singh</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.11199v2-abstract-short" style="display: inline;"> According to the holographic bound, there is only a finite density of degrees of freedom in space when gravity is taken into account. Conventional quantum field theory does not conform to this bound, since in this framework, infinitely many degrees of freedom may be localized to any given region of space. In this paper, we explore the viewpoint that quantum field theory may emerge from an underlyi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.11199v2-abstract-full').style.display = 'inline'; document.getElementById('1905.11199v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.11199v2-abstract-full" style="display: none;"> According to the holographic bound, there is only a finite density of degrees of freedom in space when gravity is taken into account. Conventional quantum field theory does not conform to this bound, since in this framework, infinitely many degrees of freedom may be localized to any given region of space. In this paper, we explore the viewpoint that quantum field theory may emerge from an underlying theory that is locally finite-dimensional, and we construct a locally finite-dimensional version of a Klein-Gordon scalar field using generalized Clifford algebras. Demanding that the finite-dimensional field operators obey a suitable version of the canonical commutation relations makes this construction essentially unique. We then find that enforcing local finite dimensionality in a holographically consistent way leads to a huge suppression of the quantum contribution to vacuum energy, to the point that the theoretical prediction becomes plausibly consistent with observations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.11199v2-abstract-full').style.display = 'none'; document.getElementById('1905.11199v2-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 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Essay written for the Gravity Research Foundation 2019 Awards for Essays on Gravitation</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> CALT-TH-2019-017 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Int. J. Mod. Phys. D Vol. 28, No. 14, 1944006 (2019) </p> </li> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Cao%2C+C&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Cao%2C+C&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Cao%2C+C&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> <div class="column"> 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