PRX Quantum最新文献_第9页

Postselection-Free Learning of Measurement-Induced Quantum Dynamics 测量诱导量子动力学的无选择后学习

PRX Quantum Pub Date : 2024-05-29 DOI: 10.1103/prxquantum.5.020347

Max McGinley

{"title":"Postselection-Free Learning of Measurement-Induced Quantum Dynamics","authors":"Max McGinley","doi":"10.1103/prxquantum.5.020347","DOIUrl":"https://doi.org/10.1103/prxquantum.5.020347","url":null,"abstract":"We address how one can empirically infer properties of quantum states generated by dynamics involving measurements. Our focus is on many-body settings where the number of measurements is extensive, making brute-force approaches based on postselection intractable due to their exponential sample complexity. We introduce a general-purpose scheme that can be used to infer any property of the postmeasurement ensemble of states (e.g., the average entanglement entropy, or frame potential) using a scalable number of experimental repetitions. We first identify a general class of “estimable properties” that can be directly extracted from experimental data. Then, based on empirical observations of such quantities, we show how one can indirectly infer information about any particular given nonestimable quantity of interest through classical postprocessing. Our approach is based on an optimization task, where one asks what are the minimum and maximum values that the desired quantity could possibly take, while ensuring consistency with observations. The true value of this quantity must then lie within a feasible range between these extrema, resulting in two-sided bounds. Narrow feasible ranges can be obtained by using a classical simulation of the device to determine which estimable properties one should measure. Even in cases where this simulation is inaccurate, unambiguous information about the true value of a given quantity realized on the quantum device can be learned. As an immediate application, we show that our method can be used to verify the emergence of quantum state designs in experiments. We identify some fundamental obstructions that in some cases prevent sharp knowledge of a given quantity from being inferred, and discuss what can be learned in cases where classical simulation is too computationally demanding to be feasible. In particular, we prove that any observer who cannot perform a classical simulation cannot distinguish the output states from those sampled from a maximally structureless ensemble.","PeriodicalId":501296,"journal":{"name":"PRX Quantum","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141197648","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}

引用次数: 0

Deterministic Generation of Qudit Photonic Graph States from Quantum Emitters 从量子发射器确定性地生成 Qudit 光子图态

PRX Quantum Pub Date : 2024-05-29 DOI: 10.1103/prxquantum.5.020346

Zahra Raissi, Edwin Barnes, Sophia E. Economou

引用次数: 0

Fault-Tolerant Code-Switching Protocols for Near-Term Quantum Processors 近端量子处理器的容错代码转换协议

PRX Quantum Pub Date : 2024-05-28 DOI: 10.1103/prxquantum.5.020345

Friederike Butt, Sascha Heußen, Manuel Rispler, Markus Müller

{"title":"Fault-Tolerant Code-Switching Protocols for Near-Term Quantum Processors","authors":"Friederike Butt, Sascha Heußen, Manuel Rispler, Markus Müller","doi":"10.1103/prxquantum.5.020345","DOIUrl":"https://doi.org/10.1103/prxquantum.5.020345","url":null,"abstract":"Topological color codes are widely acknowledged as promising candidates for fault-tolerant quantum computing. Neither a two-dimensional nor a three-dimensional topology, however, can provide a universal gate set {h, t, cnot}, with the t gate missing in the two-dimensional and the h gate in the three-dimensional case. These complementary shortcomings of the isolated topologies may be overcome in a combined approach, by switching between a two- and a three-dimensional code while maintaining the logical state. In this work, we construct resource-optimized deterministic and nondeterministic code-switching protocols for two- and three-dimensional distance-three color codes using fault-tolerant quantum circuits based on flag qubits. Deterministic protocols allow for the fault-tolerant implementation of logical gates on an encoded quantum state, while nondeterministic protocols may be used for the fault-tolerant preparation of magic states. Taking the error rates of state-of-the-art trapped-ion quantum processors as a reference, we find a logical failure probability of 3% for deterministic logical gates, which cannot be realized transversally in the respective code. By replacing the three-dimensional distance-three color code in the protocol for magic state preparation with the morphed code introduced in Vasmer and Kubica [PRX Quantum 3, 030319 (2022)], we reduce the logical failure rates by 2 orders of magnitude, thus rendering it a viable method for magic state preparation on near-term quantum processors. Our results demonstrate that code switching enables the fault-tolerant and deterministic implementation of a universal gate set under realistic conditions, and thereby provide a practical avenue to advance universal, fault-tolerant quantum computing and enable quantum algorithms on first, error-corrected logical qubits.","PeriodicalId":501296,"journal":{"name":"PRX Quantum","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141170432","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}

引用次数: 0

Site-Selective Preparation and Multistate Readout of Molecules in Optical Tweezers 光镊中分子的位点选择性制备和多态读出

PRX Quantum Pub Date : 2024-05-28 DOI: 10.1103/prxquantum.5.020344

Lewis R. B. Picard, Gabriel E. Patenotte, Annie J. Park, Samuel F. Gebretsadkan, Kang-Kuen Ni

引用次数: 0

Microwave Photon Detection at Parametric Criticality 参数临界状态下的微波光子探测

PRX Quantum Pub Date : 2024-05-24 DOI: 10.1103/prxquantum.5.020342

Kirill Petrovnin, Jiaming Wang, Michael Perelshtein, Pertti Hakonen, Gheorghe Sorin Paraoanu

引用次数: 0

Diagnostics of Mixed-State Topological Order and Breakdown of Quantum Memory 量子存储器的混合态拓扑秩序和崩溃诊断

PRX Quantum Pub Date : 2024-05-24 DOI: 10.1103/prxquantum.5.020343

Ruihua Fan, Yimu Bao, Ehud Altman, Ashvin Vishwanath

{"title":"Diagnostics of Mixed-State Topological Order and Breakdown of Quantum Memory","authors":"Ruihua Fan, Yimu Bao, Ehud Altman, Ashvin Vishwanath","doi":"10.1103/prxquantum.5.020343","DOIUrl":"https://doi.org/10.1103/prxquantum.5.020343","url":null,"abstract":"Topological quantum memory can protect information against local errors up to finite error thresholds. Such thresholds are usually determined based on the success of decoding algorithms rather than the intrinsic properties of the mixed states describing corrupted memories. Here we provide an intrinsic characterization of the breakdown of topological quantum memory, which both gives a bound on the performance of decoding algorithms and provides examples of topologically distinct mixed states. We employ three information-theoretical quantities that can be regarded as generalizations of the diagnostics of ground-state topological order, and serve as a definition for topological order in error-corrupted mixed states. We consider the topological contribution to entanglement negativity and two other metrics based on quantum relative entropy and coherent information. In the concrete example of the two-dimensional (2D) Toric code with local bit-flip and phase errors, we map three quantities to observables in 2D classical spin models and analytically show they all undergo a transition at the same error threshold. This threshold is an upper bound on that achieved in any decoding algorithm and is indeed saturated by that in the optimal decoding algorithm for the Toric code.","PeriodicalId":501296,"journal":{"name":"PRX Quantum","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141148278","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}

引用次数: 0

Quantum-Inspired Classical Algorithm for Graph Problems by Gaussian Boson Sampling 通过高斯玻色子采样解决图问题的量子启发经典算法

PRX Quantum Pub Date : 2024-05-23 DOI: 10.1103/prxquantum.5.020341

Changhun Oh, Bill Fefferman, Liang Jiang, Nicolás Quesada

{"title":"Quantum-Inspired Classical Algorithm for Graph Problems by Gaussian Boson Sampling","authors":"Changhun Oh, Bill Fefferman, Liang Jiang, Nicolás Quesada","doi":"10.1103/prxquantum.5.020341","DOIUrl":"https://doi.org/10.1103/prxquantum.5.020341","url":null,"abstract":"We present a quantum-inspired classical algorithm that can be used for graph-theoretical problems, such as finding the densest <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>k</mi></math> subgraph and finding the maximum weight clique, which are proposed as applications of a Gaussian boson sampler. The main observation from Gaussian boson samplers is that a given graph’s adjacency matrix to be encoded in a Gaussian boson sampler is non-negative and that computing the output probability of Gaussian boson sampling restricted to a non-negative adjacency matrix is thought to be strictly easier than general cases. We first provide how to program a given graph problem into our efficient classical algorithm. We then numerically compare the performance of ideal and lossy Gaussian boson samplers, our quantum-inspired classical sampler, and the uniform sampler for finding the densest <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>k</mi></math> subgraph and finding the maximum weight clique and show that the advantage from Gaussian boson samplers is not significant in general. We finally discuss the potential advantage of a Gaussian boson sampler over the proposed quantum-inspired classical sampler.","PeriodicalId":501296,"journal":{"name":"PRX Quantum","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141148307","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}

引用次数: 0

Quantum Circuits with Multiterminal Josephson-Andreev Junctions 具有多端约瑟夫森-安德烈耶夫结的量子电路

PRX Quantum Pub Date : 2024-05-22 DOI: 10.1103/prxquantum.5.020340

F.J. Matute-Cañadas, L. Tosi, A. Levy Yeyati

引用次数: 0

Editorial: Coauthor! Coauthor! 社论：共同作者合著者

PRX Quantum Pub Date : 2024-05-21 DOI: 10.1103/prxquantum.5.020001

Randall D. Kamien, Daniel Ucko

引用次数: 0

Cavity-Mediated Entanglement of Parametrically Driven Spin Qubits via Sidebands 通过边带实现腔室介导的参量驱动自旋丘比特纠缠

PRX Quantum Pub Date : 2024-05-21 DOI: 10.1103/prxquantum.5.020339

V. Srinivasa, J. M. Taylor, J. R. Petta

{"title":"Cavity-Mediated Entanglement of Parametrically Driven Spin Qubits via Sidebands","authors":"V. Srinivasa, J. M. Taylor, J. R. Petta","doi":"10.1103/prxquantum.5.020339","DOIUrl":"https://doi.org/10.1103/prxquantum.5.020339","url":null,"abstract":"We consider a pair of quantum dot-based spin qubits that interact via microwave photons in a superconducting cavity and that are also parametrically driven by separate external electric fields. For this system, we formulate a model for spin qubit entanglement in the presence of mutually off-resonant qubit and cavity frequencies. We show that the sidebands generated via the driving fields enable highly tunable qubit-qubit entanglement using only ac control and without requiring the qubit and cavity frequencies to be tuned into simultaneous resonance. The model we derive can be mapped to a variety of qubit types, including detuning-driven one-electron spin qubits in double quantum dots and three-electron resonant exchange qubits in triple quantum dots. The high degree of nonlinearity inherent in spin qubits renders these systems particularly favorable for parametric drive-activated entanglement. We determine multiple common resonance conditions for the two driven qubits and the cavity and identify experimentally relevant parameter regimes that enable the implementation of entangling gates with suppressed sensitivity to cavity photon occupation and decay. The parametrically driven sideband resonance approach that we describe provides a promising route toward scalability and modularity in spin-based quantum information processing through drive-enabled tunability that can also be implemented in micromagnet-free electron and hole systems for spin-photon coupling.","PeriodicalId":501296,"journal":{"name":"PRX Quantum","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141148515","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}

引用次数: 0