Pub Date : 2023-11-13DOI: 10.1103/prxquantum.4.040325
Alexander M. Dalzell, B. David Clader, Grant Salton, Mario Berta, Cedric Yen-Yu Lin, David A. Bader, Nikitas Stamatopoulos, Martin J. A. Schuetz, Fernando G. S. L. Brandão, Helmut G. Katzgraber, William J. Zeng
A detailed resource analysis of an established quantum algorithm for convex optimization reveals that the practical run times implied by this quantum solution are impractical for problems of interest in finance.
{"title":"End-To-End Resource Analysis for Quantum Interior-Point Methods and Portfolio Optimization","authors":"Alexander M. Dalzell, B. David Clader, Grant Salton, Mario Berta, Cedric Yen-Yu Lin, David A. Bader, Nikitas Stamatopoulos, Martin J. A. Schuetz, Fernando G. S. L. Brandão, Helmut G. Katzgraber, William J. Zeng","doi":"10.1103/prxquantum.4.040325","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040325","url":null,"abstract":"A detailed resource analysis of an established quantum algorithm for convex optimization reveals that the practical run times implied by this quantum solution are impractical for problems of interest in finance.","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136283837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-09DOI: 10.1103/prxquantum.4.040324
Karthik Siva, Gerwin Koolstra, John Steinmetz, William P. Livingston, Debmalya Das, L. Chen, J.M. Kreikebaum, N.J. Stevenson, C. Jünger, D.I. Santiago, I. Siddiqi, A.N. Jordan
Continuous weak measurements enable reconstruction of time-dependent Hamiltonians, enhancing the time resolution of quantum gate errors beyond what is revealed by standard tomographic and benchmarking techniques.
{"title":"Time-Dependent Hamiltonian Reconstruction Using Continuous Weak Measurements","authors":"Karthik Siva, Gerwin Koolstra, John Steinmetz, William P. Livingston, Debmalya Das, L. Chen, J.M. Kreikebaum, N.J. Stevenson, C. Jünger, D.I. Santiago, I. Siddiqi, A.N. Jordan","doi":"10.1103/prxquantum.4.040324","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040324","url":null,"abstract":"Continuous weak measurements enable reconstruction of time-dependent Hamiltonians, enhancing the time resolution of quantum gate errors beyond what is revealed by standard tomographic and benchmarking techniques.","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135291404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-08DOI: 10.1103/prxquantum.4.040323
Jorge Miguel-Ramiro, Ferran Riera-Sàbat, Wolfgang Dür
W states are a valuable resource for various quantum information tasks, and several protocols to generate them have been proposed and implemented. We introduce a quantum repeater protocol to efficiently distribute three-qubit W states over arbitrary distances in a two-dimensional triangular quantum network with polylogarithmic overhead, thereby enabling these applications between remote parties. The repeater protocol combines two ingredients that we establish: probabilistic entanglement swapping with three copies of three-qubit W states to a single long-distance three-qubit W state, and an improved entanglement purification protocol. The latter not only shows a better performance, but also an enlarged purification regime as compared to previous approaches. We show that the repeater protocol allows one to deal with errors resulting from imperfect channels or state preparation, and noisy operations, and we analyze error thresholds, achievable fidelities, and overheads.Received 2 May 2023Revised 8 September 2023Accepted 4 October 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040323Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum communicationQuantum networksQuantum protocolsQuantum repeatersQuantum Information, Science & Technology
{"title":"Quantum Repeater for W States","authors":"Jorge Miguel-Ramiro, Ferran Riera-Sàbat, Wolfgang Dür","doi":"10.1103/prxquantum.4.040323","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040323","url":null,"abstract":"W states are a valuable resource for various quantum information tasks, and several protocols to generate them have been proposed and implemented. We introduce a quantum repeater protocol to efficiently distribute three-qubit W states over arbitrary distances in a two-dimensional triangular quantum network with polylogarithmic overhead, thereby enabling these applications between remote parties. The repeater protocol combines two ingredients that we establish: probabilistic entanglement swapping with three copies of three-qubit W states to a single long-distance three-qubit W state, and an improved entanglement purification protocol. The latter not only shows a better performance, but also an enlarged purification regime as compared to previous approaches. We show that the repeater protocol allows one to deal with errors resulting from imperfect channels or state preparation, and noisy operations, and we analyze error thresholds, achievable fidelities, and overheads.Received 2 May 2023Revised 8 September 2023Accepted 4 October 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040323Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum communicationQuantum networksQuantum protocolsQuantum repeatersQuantum Information, Science & Technology","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135341672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-06DOI: 10.1103/prxquantum.4.040322
Paul Hilaire, Yaron Castor, Edwin Barnes, Sophia E. Economou, Frédéric Grosshans
Quantum threshold theorems impose hard limits on the hardware capabilities to process quantum information. We derive tight and fundamental upper bounds to loss-tolerance thresholds in different linear-optical quantum information processing settings through an adversarial framework, taking into account the intrinsically probabilistic nature of linear optical Bell measurements. For logical Bell state measurements—ubiquitous operations in photonic quantum information—we demonstrate analytically that linear optics can achieve the fundamental loss threshold imposed by the no-cloning theorem even though, following the work of Lee et al. [Phys. Rev. A 100, 052303 (2019)] the constraint was widely assumed to be stricter. We spotlight the assumptions of the latter publication and find their bound holds for a logical Bell measurement built from adaptive physical linear-optical Bell measurements. We also give an explicit even stricter bound for nonadaptive Bell measurements.7 MoreReceived 21 February 2023Revised 22 May 2023Accepted 22 September 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040322Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasIntegrated opticsQuantum communicationQuantum error correctionQuantum foundationsQuantum information theoryQuantum Information, Science & TechnologyAtomic, Molecular & Optical
量子阈值定理对处理量子信息的硬件能力施加了硬性限制。考虑到线性光学贝尔测量的内在概率性质，我们通过对抗性框架推导出不同线性光学量子信息处理设置中损失容忍阈值的严格和基本上界。对于逻辑贝尔态测量——光子量子信息中无处不在的操作——我们分析地证明了线性光学可以达到不可克隆定理所施加的基本损失阈值，尽管在Lee等人的工作之后。Rev. A 100,052303(2019)]的约束被普遍认为更严格。我们重点介绍了后一出版物的假设，并找到了自适应物理线性光学贝尔测量建立的逻辑贝尔测量的界持有。对于非自适应贝尔测量，我们也给出了一个明确的更严格的界根据知识共享署名4.0国际许可协议，美国物理学会于2023年9月22日接受doi:https://doi.org/10.1103/PRXQuantum.4.040322Published。这项工作的进一步分发必须保持作者的归属和已发表文章的标题，期刊引用和DOI。发表于美国物理学会物理学科标题(PhySH)研究领域集成光学量子通信量子纠错量子基础量子信息理论量子信息科学与技术原子分子光学
{"title":"Linear Optical Logical Bell State Measurements with Optimal Loss-Tolerance Threshold","authors":"Paul Hilaire, Yaron Castor, Edwin Barnes, Sophia E. Economou, Frédéric Grosshans","doi":"10.1103/prxquantum.4.040322","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040322","url":null,"abstract":"Quantum threshold theorems impose hard limits on the hardware capabilities to process quantum information. We derive tight and fundamental upper bounds to loss-tolerance thresholds in different linear-optical quantum information processing settings through an adversarial framework, taking into account the intrinsically probabilistic nature of linear optical Bell measurements. For logical Bell state measurements—ubiquitous operations in photonic quantum information—we demonstrate analytically that linear optics can achieve the fundamental loss threshold imposed by the no-cloning theorem even though, following the work of Lee et al. [Phys. Rev. A 100, 052303 (2019)] the constraint was widely assumed to be stricter. We spotlight the assumptions of the latter publication and find their bound holds for a logical Bell measurement built from adaptive physical linear-optical Bell measurements. We also give an explicit even stricter bound for nonadaptive Bell measurements.7 MoreReceived 21 February 2023Revised 22 May 2023Accepted 22 September 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040322Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasIntegrated opticsQuantum communicationQuantum error correctionQuantum foundationsQuantum information theoryQuantum Information, Science & TechnologyAtomic, Molecular & Optical","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135584655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-03DOI: 10.1103/prxquantum.4.040321
Ilya A. Simakov, Grigoriy S. Mazhorin, Ilya N. Moskalenko, Nikolay N. Abramov, Alexander A. Grigorev, Dmitry O. Moskalev, Anastasiya A. Pishchimova, Nikita S. Smirnov, Evgeniy V. Zikiy, Ilya A. Rodionov, Ilya S. Besedin
Tunable couplers have recently become one of the most powerful tools for implementing two-qubit gates between superconducting qubits. A tunable coupler typically includes a nonlinear element, such as a superconducting quantum interference device, which is used to tune the resonance frequency of an LC circuit connecting two qubits. Here we propose a complimentary approach where instead of tuning the resonance frequency of the tunable coupler by applying a quasistatic control signal, we excite by microwave the degree of freedom associated with the coupler itself. Because of strong effective longitudinal coupling between the coupler and the qubits, the frequency of this transition strongly depends on the computational state, leading to different phase accumulations in different states. Using this method, we experimentally demonstrate a controlled-Z gate of 44-ns duration on a fluxonium-based quantum processor, obtaining a fidelity of 97.6%±0.4% characterized by cross-entropy benchmarking.2 MoreReceived 22 February 2023Accepted 5 October 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040321Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum gatesPhysical SystemsSuperconducting qubitsCondensed Matter, Materials & Applied Physics
{"title":"Coupler Microwave-Activated Controlled-Phase Gate on Fluxonium Qubits","authors":"Ilya A. Simakov, Grigoriy S. Mazhorin, Ilya N. Moskalenko, Nikolay N. Abramov, Alexander A. Grigorev, Dmitry O. Moskalev, Anastasiya A. Pishchimova, Nikita S. Smirnov, Evgeniy V. Zikiy, Ilya A. Rodionov, Ilya S. Besedin","doi":"10.1103/prxquantum.4.040321","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040321","url":null,"abstract":"Tunable couplers have recently become one of the most powerful tools for implementing two-qubit gates between superconducting qubits. A tunable coupler typically includes a nonlinear element, such as a superconducting quantum interference device, which is used to tune the resonance frequency of an LC circuit connecting two qubits. Here we propose a complimentary approach where instead of tuning the resonance frequency of the tunable coupler by applying a quasistatic control signal, we excite by microwave the degree of freedom associated with the coupler itself. Because of strong effective longitudinal coupling between the coupler and the qubits, the frequency of this transition strongly depends on the computational state, leading to different phase accumulations in different states. Using this method, we experimentally demonstrate a controlled-Z gate of 44-ns duration on a fluxonium-based quantum processor, obtaining a fidelity of 97.6%±0.4% characterized by cross-entropy benchmarking.2 MoreReceived 22 February 2023Accepted 5 October 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040321Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum gatesPhysical SystemsSuperconducting qubitsCondensed Matter, Materials & Applied Physics","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135869038","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1103/prxquantum.4.040320
Masoud Ghalaii, Sima Bahrani, Carlo Liorni, Federico Grasselli, Hermann Kampermann, Lewis Wooltorton, Rupesh Kumar, Stefano Pirandola, Timothy P. Spiller, Alexander Ling, Bruno Huttner, Mohsen Razavi
The security of prepare-and-measure satellite-based quantum key distribution (QKD), under restricted eavesdropping scenarios, is addressed. We particularly consider cases where the eavesdropper, Eve, has limited access to the transmitted signal by Alice and/or Bob’s receiver station. This restriction is modeled by lossy channels between relevant parties, where the transmissivity of such channels can, in principle, be bounded by monitoring techniques. An artifact of such lossy channels is the possibility of having bypass channels, those that are not accessible to Eve but that may not necessarily be characterized by the users either. This creates interesting unexplored scenarios for analyzing QKD security. In this paper, we obtain generic bounds on the key rate in the presence of bypass channels and apply them to continuous-variable QKD protocols with Gaussian encoding with direct and reverse reconciliation. We find regimes of operation in which the above restrictions on Eve can considerably improve system performance. We also develop customized bounds for several protocols in the BB84 family and show that, in certain regimes, even the simple protocol of BB84 with weak coherent pulses is able to offer positive key rates at high channel losses, which would otherwise be impossible under an unrestricted Eve. In this case, the limitation on Eve would allow Alice to send signals with larger intensities than the optimal value under an ideal Eve, which effectively reduces the effective channel loss. In all these cases, the part of the transmitted signal that does not reach Eve can play a nontrivial role in specifying the achievable key rate. Our work opens up new security frameworks for spaceborne quantum communications systems.10 MoreReceived 20 December 2022Revised 28 April 2023Accepted 25 September 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040320Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum communication, protocols & technologyQuantum Information, Science & Technology
{"title":"Satellite-Based Quantum Key Distribution in the Presence of Bypass Channels","authors":"Masoud Ghalaii, Sima Bahrani, Carlo Liorni, Federico Grasselli, Hermann Kampermann, Lewis Wooltorton, Rupesh Kumar, Stefano Pirandola, Timothy P. Spiller, Alexander Ling, Bruno Huttner, Mohsen Razavi","doi":"10.1103/prxquantum.4.040320","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040320","url":null,"abstract":"The security of prepare-and-measure satellite-based quantum key distribution (QKD), under restricted eavesdropping scenarios, is addressed. We particularly consider cases where the eavesdropper, Eve, has limited access to the transmitted signal by Alice and/or Bob’s receiver station. This restriction is modeled by lossy channels between relevant parties, where the transmissivity of such channels can, in principle, be bounded by monitoring techniques. An artifact of such lossy channels is the possibility of having bypass channels, those that are not accessible to Eve but that may not necessarily be characterized by the users either. This creates interesting unexplored scenarios for analyzing QKD security. In this paper, we obtain generic bounds on the key rate in the presence of bypass channels and apply them to continuous-variable QKD protocols with Gaussian encoding with direct and reverse reconciliation. We find regimes of operation in which the above restrictions on Eve can considerably improve system performance. We also develop customized bounds for several protocols in the BB84 family and show that, in certain regimes, even the simple protocol of BB84 with weak coherent pulses is able to offer positive key rates at high channel losses, which would otherwise be impossible under an unrestricted Eve. In this case, the limitation on Eve would allow Alice to send signals with larger intensities than the optimal value under an ideal Eve, which effectively reduces the effective channel loss. In all these cases, the part of the transmitted signal that does not reach Eve can play a nontrivial role in specifying the achievable key rate. Our work opens up new security frameworks for spaceborne quantum communications systems.10 MoreReceived 20 December 2022Revised 28 April 2023Accepted 25 September 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040320Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum communication, protocols & technologyQuantum Information, Science & Technology","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135326088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-30DOI: 10.1103/prxquantum.4.040319
Marco Fellous-Asiani, Jing Hao Chai, Yvain Thonnart, Hui Khoon Ng, Robert S. Whitney, Alexia Auffèves
In the race to build scalable quantum computers, minimizing the resource consumption of their full stack to achieve a target performance becomes crucial. It mandates a synergy of fundamental physics and engineering: the former for the microscopic aspects of computing performance and the latter for the macroscopic resource consumption. For this, we propose a holistic methodology dubbed metric noise resource (MNR) that is able to quantify and optimize all aspects of the full-stack quantum computer, bringing together concepts from quantum physics (e.g., noise on the qubits), quantum information (e.g., computing architecture and type of error correction), and enabling technologies (e.g., cryogenics, control electronics, and wiring). This holistic approach allows us to define and study resource efficiencies as ratios between performance and resource cost. As a proof of concept, we use MNR to minimize the power consumption of a full-stack quantum computer, performing noisy or fault-tolerant computing with a target performance for the task of interest. Comparing this with a classical processor performing the same task, we identify a quantum energy advantage in regimes of parameters distinct from the commonly considered quantum computational advantage. This provides a previously overlooked practical argument for building quantum computers. While our illustration uses highly idealized parameters inspired by superconducting qubits with concatenated error correction, the methodology is universal—it applies to other qubits and error-correcting codes—and it provides experimenters with guidelines to build energy-efficient quantum computers. In some regimes of high energy consumption, it can reduce this consumption by orders of magnitude. Overall, our methodology lays the theoretical foundation for resource-efficient quantum technologies.7 MoreReceived 29 November 2022Accepted 31 July 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040319Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEnergy-efficient infrastructureQuantum algorithmsQuantum benchmarkingQuantum computationQuantum engineeringQuantum error correctionQuantum gatesQuantum information architectures & platformsQuantum information processingQuantum softwareQuantum Information, Science & TechnologyInterdisciplinary Physics
{"title":"Optimizing Resource Efficiencies for Scalable Full-Stack Quantum Computers","authors":"Marco Fellous-Asiani, Jing Hao Chai, Yvain Thonnart, Hui Khoon Ng, Robert S. Whitney, Alexia Auffèves","doi":"10.1103/prxquantum.4.040319","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040319","url":null,"abstract":"In the race to build scalable quantum computers, minimizing the resource consumption of their full stack to achieve a target performance becomes crucial. It mandates a synergy of fundamental physics and engineering: the former for the microscopic aspects of computing performance and the latter for the macroscopic resource consumption. For this, we propose a holistic methodology dubbed metric noise resource (MNR) that is able to quantify and optimize all aspects of the full-stack quantum computer, bringing together concepts from quantum physics (e.g., noise on the qubits), quantum information (e.g., computing architecture and type of error correction), and enabling technologies (e.g., cryogenics, control electronics, and wiring). This holistic approach allows us to define and study resource efficiencies as ratios between performance and resource cost. As a proof of concept, we use MNR to minimize the power consumption of a full-stack quantum computer, performing noisy or fault-tolerant computing with a target performance for the task of interest. Comparing this with a classical processor performing the same task, we identify a quantum energy advantage in regimes of parameters distinct from the commonly considered quantum computational advantage. This provides a previously overlooked practical argument for building quantum computers. While our illustration uses highly idealized parameters inspired by superconducting qubits with concatenated error correction, the methodology is universal—it applies to other qubits and error-correcting codes—and it provides experimenters with guidelines to build energy-efficient quantum computers. In some regimes of high energy consumption, it can reduce this consumption by orders of magnitude. Overall, our methodology lays the theoretical foundation for resource-efficient quantum technologies.7 MoreReceived 29 November 2022Accepted 31 July 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040319Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEnergy-efficient infrastructureQuantum algorithmsQuantum benchmarkingQuantum computationQuantum engineeringQuantum error correctionQuantum gatesQuantum information architectures & platformsQuantum information processingQuantum softwareQuantum Information, Science & TechnologyInterdisciplinary Physics","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136017917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-27DOI: 10.1103/prxquantum.4.040318
Jielun Chen, E.M. Stoudenmire, Steven R. White
The quantum Fourier transform (QFT) is a key component of many important quantum algorithms, most famously being the essential ingredient in Shor’s algorithm for factoring products of primes. Given its remarkable capability, one would think it can introduce large entanglement to qubit systems and would be difficult to simulate classically. While early results showed the QFT indeed has maximal operator entanglement, we show that this is entirely due to the bit reversal in the QFT. The core part of the QFT has Schmidt coefficients decaying exponentially quickly, and thus it can generate only a constant amount of entanglement regardless of the number of qubits. In addition, we show the entangling power of the QFT is the same as the time evolution of a Hamiltonian with exponentially decaying interactions, and thus a variant of the area law for dynamics can be used to understand the low entanglement intuitively. Using the low entanglement property of the QFT, we show that classical simulations of the QFT on a matrix product state with low bond dimension take time linear in the number of qubits, providing a potential speedup over the classical fast Fourier transform on many classes of functions. We demonstrate this speedup in test calculations on some simple functions. For data vectors of length 106–108, the speedup can be a few orders of magnitude.2 MoreReceived 2 January 2023Accepted 25 September 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040318Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEntanglement entropyEntanglement measuresEntanglement productionQuantum algorithms & computationQuantum circuitsQuantum computationQuantum correlations in quantum informationQuantum correlations, foundations & formalismQuantum entanglementQuantum information theoryTechniquesMatrix product statesTensor network methodsQuantum Information, Science & TechnologyEnergy Science & Technology
{"title":"Quantum Fourier Transform Has Small Entanglement","authors":"Jielun Chen, E.M. Stoudenmire, Steven R. White","doi":"10.1103/prxquantum.4.040318","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040318","url":null,"abstract":"The quantum Fourier transform (QFT) is a key component of many important quantum algorithms, most famously being the essential ingredient in Shor’s algorithm for factoring products of primes. Given its remarkable capability, one would think it can introduce large entanglement to qubit systems and would be difficult to simulate classically. While early results showed the QFT indeed has maximal operator entanglement, we show that this is entirely due to the bit reversal in the QFT. The core part of the QFT has Schmidt coefficients decaying exponentially quickly, and thus it can generate only a constant amount of entanglement regardless of the number of qubits. In addition, we show the entangling power of the QFT is the same as the time evolution of a Hamiltonian with exponentially decaying interactions, and thus a variant of the area law for dynamics can be used to understand the low entanglement intuitively. Using the low entanglement property of the QFT, we show that classical simulations of the QFT on a matrix product state with low bond dimension take time linear in the number of qubits, providing a potential speedup over the classical fast Fourier transform on many classes of functions. We demonstrate this speedup in test calculations on some simple functions. For data vectors of length 106–108, the speedup can be a few orders of magnitude.2 MoreReceived 2 January 2023Accepted 25 September 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040318Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEntanglement entropyEntanglement measuresEntanglement productionQuantum algorithms & computationQuantum circuitsQuantum computationQuantum correlations in quantum informationQuantum correlations, foundations & formalismQuantum entanglementQuantum information theoryTechniquesMatrix product statesTensor network methodsQuantum Information, Science & TechnologyEnergy Science & Technology","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136234200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We introduce a method to measure many-body magic in quantum systems based on a statistical exploration of Pauli strings via Markov chains. We demonstrate that sampling such Pauli-Markov chains gives ample flexibility in terms of partitions where to sample from: in particular, it enables the efficient extraction of the magic contained in the correlations between widely separated subsystems, which characterizes the nonlocality of magic. Our method can be implemented in a variety of situations. We describe an efficient sampling procedure using tree tensor networks, that exploit their hierarchical structure leading to a modest O(logN) computational scaling with system size. To showcase the applicability and efficiency of our method, we demonstrate the importance of magic in many-body systems via the following discoveries: (a) for one-dimensional systems, we show that long-range magic displays strong signatures of conformal quantum criticality (Ising, Potts, and Gaussian), overcoming the limitations of full state magic; (b) in two-dimensional Z2 lattice gauge theories, we provide conclusive evidence that magic is able to identify the confinement-deconfinement transition, and displays critical scaling behavior even at relatively modest volumes. Finally, we discuss an experimental implementation of the method, which relies only on measurements of Pauli observables.8 MoreReceived 13 June 2023Accepted 26 September 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040317Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLattice gauge theoryPhase transitionsQuantum information theoryQuantum simulationResource theoriesTechniquesTensor network methodsQuantum Information, Science & Technology
{"title":"Many-Body Magic Via Pauli-Markov Chains—From Criticality to Gauge Theories","authors":"Poetri Sonya Tarabunga, Emanuele Tirrito, Titas Chanda, Marcello Dalmonte","doi":"10.1103/prxquantum.4.040317","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040317","url":null,"abstract":"We introduce a method to measure many-body magic in quantum systems based on a statistical exploration of Pauli strings via Markov chains. We demonstrate that sampling such Pauli-Markov chains gives ample flexibility in terms of partitions where to sample from: in particular, it enables the efficient extraction of the magic contained in the correlations between widely separated subsystems, which characterizes the nonlocality of magic. Our method can be implemented in a variety of situations. We describe an efficient sampling procedure using tree tensor networks, that exploit their hierarchical structure leading to a modest O(logN) computational scaling with system size. To showcase the applicability and efficiency of our method, we demonstrate the importance of magic in many-body systems via the following discoveries: (a) for one-dimensional systems, we show that long-range magic displays strong signatures of conformal quantum criticality (Ising, Potts, and Gaussian), overcoming the limitations of full state magic; (b) in two-dimensional Z2 lattice gauge theories, we provide conclusive evidence that magic is able to identify the confinement-deconfinement transition, and displays critical scaling behavior even at relatively modest volumes. Finally, we discuss an experimental implementation of the method, which relies only on measurements of Pauli observables.8 MoreReceived 13 June 2023Accepted 26 September 2023DOI:https://doi.org/10.1103/PRXQuantum.4.040317Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLattice gauge theoryPhase transitionsQuantum information theoryQuantum simulationResource theoriesTechniquesTensor network methodsQuantum Information, Science & Technology","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136376393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bosonic cat qubits stabilized with a driven two-photon dissipation are systems with exponentially biased noise, opening the door to low-overhead, fault-tolerant and universal quantum computing. However, current gate proposals for such qubits induce substantial noise of the unprotected type, whose poor scaling with the relevant experimental parameters limits their practical use. In this work, we provide a new perspective on dissipative cat qubits by reconsidering the reservoir mode used to engineer the tailored two-photon dissipation, and show how it can be leveraged to mitigate gate-induced errors. Doing so, we introduce four new designs of high-fidelity and bias-preserving cat qubit gates, and compare them to the prevalent gate methods. These four designs should give a broad overview of gate engineering for dissipative systems with different and complementary ideas. In particular, we propose both already achievable low-error gate designs and longer-term implementations.
{"title":"Designing High-Fidelity Zeno Gates for Dissipative Cat Qubits","authors":"Gautier, Ronan, Mirrahimi, Mazyar, Sarlette, Alain","doi":"10.1103/prxquantum.4.040316","DOIUrl":"https://doi.org/10.1103/prxquantum.4.040316","url":null,"abstract":"Bosonic cat qubits stabilized with a driven two-photon dissipation are systems with exponentially biased noise, opening the door to low-overhead, fault-tolerant and universal quantum computing. However, current gate proposals for such qubits induce substantial noise of the unprotected type, whose poor scaling with the relevant experimental parameters limits their practical use. In this work, we provide a new perspective on dissipative cat qubits by reconsidering the reservoir mode used to engineer the tailored two-photon dissipation, and show how it can be leveraged to mitigate gate-induced errors. Doing so, we introduce four new designs of high-fidelity and bias-preserving cat qubit gates, and compare them to the prevalent gate methods. These four designs should give a broad overview of gate engineering for dissipative systems with different and complementary ideas. In particular, we propose both already achievable low-error gate designs and longer-term implementations.","PeriodicalId":74587,"journal":{"name":"PRX quantum : a Physical Review journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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