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arXiv 2022年

作者： Pan, Minghua Wang, Bin Tao, Xiaoling Zheng, Shenggen Situ, Haozhen Li, Lvzhou Guangxi Key Laboratory of Cryptography and Information Security Guilin University of Electronic Technology Guilin541004 China Peng Cheng Laboratory Shenzhen518055 China College of Mathematics and Informatics South China Agricultural University Guangzhou510642 China Institute of Quantum Computing and Software School of Computer Science and Engineering Sun Yat-sen University Guangzhou510006 China

quantum computing holds tremendous potential for processing high-dimensional data, capitalizing on the unique capabilities of superposition and parallelism within quantum states. As we navigate the noisy intermediate-scale quantum (NISQ) era, the exploration of quantum computing applications has emerged as a compelling frontier. One area of particular interest within the realm of cyberspace security is Behavior Detection and Evaluation (BDE). Notably, the detection and evaluation of internal abnormal behaviors pose significant challenges, given their infrequent occurrence or even their concealed nature amidst vast volumes of normal data. In this paper, we introduce a novel quantum behavior detection and evaluation algorithm (QBDE) tailored for internal user analysis. The QBDE algorithm comprises a quantum Generative Adversarial Network (QGAN) in conjunction with a classical neural network for detection and evaluation tasks. The QGAN is built upon a hybrid architecture, encompassing a quantum Generator (GQ) and a Classical Discriminator (DC). GQ, designed as a parameterized quantum circuit (PQC), collaborates with DC, a classical neural network, to collectively enhance the analysis process. To address the challenge of imbalanced positive and negative samples, GQ is employed to generate negative samples. Both GQ and DC are optimized through gradient descent techniques. Through extensive simulation tests and quantitative analyses, we substantiate the effectiveness of the QBDE algorithm in detecting and evaluating internal user abnormal behaviors. Our work not only introduces a novel approach to abnormal behavior detection and evaluation but also pioneers a new application scenario for quantum algorithms. This paradigm shift underscores the promising prospects of quantum computing in tackling complex cybersecurity challenges. Copyright © 2022, The Authors. All rights reserved.

关键词： Generative adversarial networks

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Self-Testing of a Single quantum System: theory and Experiment

arXiv

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arXiv 2022年

作者： Hu, Xiao-Min Xie, Yi Arora, Atul Singh Ai, Ming-Zhong Bharti, Kishor Zhang, Jie Wu, Wei Chen, Ping-Xing Cui, Jin-Ming Liu, Bi-Heng Huang, Yun-Feng Li, Chuan-Feng Guo, Guang-Can Roland, Jérémie Cabello, Adán Kwek, Leong-Chuan CAS Key Laboratory of Quantum Information University of Science and Technology of China Hefei230026 China CAS Center For Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei230026 China Department of Physics College of Liberal Arts and Sciences National University of Defense Technology Hunan Changsha410073 China Interdisciplinary Center for Quantum Information National University of Defense Technology Hunan Changsha410073 China Université libre de Bruxelles Belgium Institute of Quantum Information and Matter Department of Computing and Mathematical Sciences California Institute of Technology United States Centre for Quantum Technologies National University of Singapore Singapore Joint Center for Quantum Information and Computer Science Joint Quantum Institute NIST University of Maryland College ParkMD20742 United States Departamento de Física Aplicada II Universidad de Sevilla SevillaE-41012 Spain Instituto Carlos I de Física Teórica y Computacional Universidad de Sevilla SevillaE-41012 Spain MajuLab CNRS-UNS-NUS-NTU International Joint Research Unit UMI 3654 Singapore Singapore National Institute of Education Nanyang Technological University Singapore637616 Singapore

Certifying individual quantum devices with minimal assumptions is crucial for the development of quantum technologies. Here, we investigate how to leverage single-system contextuality to realize self-testing. We develop a robust self-testing protocol based on the simplest contextuality witness for the simplest contextual quantum system, the Klyachko-Can-Binicioğlu-Shumovsky (KCBS) inequality for the qutrit. We establish a lower bound on the fidelity of the state and the measurements (to an ideal configuration) as a function of the value of the witness under a pragmatic assumption on the measurements we call the KCBS orthogonality condition. We apply the method in an experiment with randomly chosen measurements on a single trapped 40Ca+ and near-perfect detection efficiency. The observed statistics allow us to self-test the system and provide the first experimental demonstration of quantum self-testing of a single system. Further, we quantify and report that deviations from our assumptions are minimal, an aspect previously overlooked by contextuality experiments. Copyright © 2022, The Authors. All rights reserved.

关键词： quantum optics

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Nonequilibrium dynamics of the localization-delocalization transition in the non-Hermitian Aubry-André model

arXiv

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arXiv 2022年

作者： Zhai, Liang-Jun Huang, Guang-Yao Yin, Shuai Department of Physics Nanjing University Nanjing210093 China The School of Mathematics and Physics Jiangsu University of Technology Changzhou213001 China Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha410073 China School of Physics Sun Yat-Sen University Guangzhou510275 China

In this paper, we investigate the driven dynamics of the localization transition in the non-Hermitian Aubry-André model with the periodic boundary condition. Depending on the strength of the quasi-periodic potential λ, this model undergoes a localization-delocalization phase transition. We find that the localization length ξ satisfies ξ ∼ Ε−ν with Ε being the distance from the critical point and ν = 1 being a universal critical exponent independent of the non-Hermitian parameter. In addition, from the finite-size scaling of the energy gap between the ground state and the first excited state, we determine the dynamic exponent z as z = 2. The critical exponent of the inverse participation ratio (IPR) for the nth eigenstate is also determined as s = 0.1197. By changing Ε linearly to cross the critical point, we find that the driven dynamics can be described by the Kibble-Zurek scaling (KZS). Moreover, we show that the KZS with the same set of the exponents can be generalized to the localization phase transitions in the excited states. Copyright © 2022, The Authors. All rights reserved.

关键词： Excited states

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Hamiltonian simulation with random inputs

arXiv

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arXiv 2021年

作者： Zhao, Qi Zhou, You Shaw, Alexander F. Li, Tongyang Childs, Andrew M. Joint Center for Quantum Information and Computer Science University of Maryland College ParkMD20742 United States Nanyang Quantum Hub School of Physical and Mathematical Sciences Nanyang Technological University 637371 Singapore Center on Frontiers of Computing Studies Peking University Beijing100871 China School of Computer Science Peking University Beijing100871 China Center for Theoretical Physics Massachusetts Institute of Technology CambridgeMA02139 United States Department of Computer Science Institute for Advanced Computer Studies University of Maryland College ParkMD20742 United States

The algorithmic error of digital quantum simulations is usually explored in terms of the spectral norm distance between the actual and ideal evolution operators. In practice, this worst-case error analysis may be unnecessarily pessimistic. To address this, we develop a theory of average-case performance of Hamiltonian simulation with random initial states. We relate the average-case error to the Frobenius norm of the multiplicative error and give upper bounds for the product formula (PF) and truncated Taylor series methods. As applications, we estimate average-case error for digital Hamiltonian simulation of general lattice Hamiltonians and k-local Hamiltonians. In particular, for the nearest-neighbor Heisenberg chain with n spins, the error is quadratically reduced from O(n) in the worst case to O(√n) on average for both the PF method and the Taylor series method. Numerical evidence suggests that this theory accurately characterizes the average error for concrete models. We also apply our results to error analysis in the simulation of quantum scrambling. Copyright © 2021, The Authors. All rights reserved.

关键词： Hamiltonians

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Neural Posterior Estimation with guaranteed exact coverage: the ringdown of GW150914

arXiv

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arXiv 2023年

作者： Crisostomi, Marco Dey, Kallol Barausse, Enrico Trotta, Roberto SISSA Via Bonomea 265 Trieste34136 Italy INFN Sezione di Trieste Italy IFPU - Institute for Fundamental Physics of the Universe Via Beirut 2 Trieste34014 Italy School of Physics Indian Institute of Science Education and Research Thiruvananthapuram Maruthamala PO Vithura Kerala Thiruvananthapuram695551 India Physics Department Imperial College London Prince Consort Rd LondonSW7 2AZ United Kingdom Centro Nazionale "High Performance Computer Big Data and Quantum Computing" Italy

We analyze the ringdown phase of the first detected black-hole merger, GW150914, using a simulation-based inference pipeline based on masked autoregressive flows. We obtain approximate marginal posterior distributions for the ringdown parameters, namely the mass, spin, and the amplitude and phases of the dominant mode and its first overtone. Thanks to the locally amortized nature of our method, we are able to calibrate our posteriors with injected simulations, producing posterior regions with guaranteed (i.e. exact) frequentist coverage of the true values. For GW150914, our calibrated posteriors provide only mild evidence (∼ 2σ) for the presence of an overtone, even if the ringdown is assumed to start at the peak of the amplitude. Copyright © 2023, The Authors. All rights reserved.

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Efficient experimental verification of quantum gates with local operations

arXiv

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arXiv 2021年

作者： Zhang, Rui-Qi Hou, Zhibo Tang, Jun-Feng Shang, Jiangwei Zhu, Huangjun Xiang, Guo-Yong Li, Chuan-Feng Guo, Guang-Can Key Laboratory of Quantum Information University of Science and Technology of China CAS Hefei230026 China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei230026 China Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement of Ministry of Education School of Physics Beijing Institute of Technology Beijing100081 China State Key Laboratory of Surface Physics Department of Physics Fudan University Shanghai200433 China Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai200433 China Center for Field Theory and Particle Physics Fudan University Shanghai200433 China

Verifying the correct functioning of quantum gates is a crucial step towards reliable quantum information processing, but it becomes an overwhelming challenge as the system size grows due to the dimensionality curse. Recent theoretical breakthroughs show that it is possible to verify various important quantum gates with the optimal sample complexity of O(1/Ε) using local operations only, where Ε is the estimation precision. In this work, we propose a variant of quantum gate verification (QGV) which is robust to practical gate imperfections, and experimentally realize efficient QGV on a two-qubit controlled-not gate and a three-qubit Toffoli gate using only local state preparations and measurements. The experimental results show that, by using only 1600 and 2600 measurements on average, we can verify with 95% confidence level that the implemented controlled-not gate and Toffoli gate have fidelities at least 99% and 97%, respectively. Demonstrating the superior low sample complexity and experimental feasibility of QGV, our work promises a solution to the dimensionality curse in verifying large quantum devices in the quantum era. Copyright © 2021, The Authors. All rights reserved.

关键词： Qubits

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quantum recurrences in the kicked top

arXiv

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arXiv 2023年

作者： Anand, Amit Davis, Jack Ghose, Shohini Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Department of Physics and Computer Science Wilfrid Laurier University WaterlooONN2L 3C5 Canada Perimeter Institute for Theoretical Physics 31 Caroline St N WaterlooONN2L 2Y5 Canada

The correspondence principle plays an important role in understanding the emergence of classical chaos from an underlying quantum mechanics. Here we present an infinite family of quantum dynamics that never resembles the analogous classical chaotic dynamics irrespective of dimension. These take the form of stroboscopic unitary evolutions in the quantum kicked top that act as the identity after a finite number of kicks. Because these state-independent temporal periodicities are present in all dimensions, their existence represents a universal violation of the correspondence principle. We further discuss the relationship of these periodicities with the quantum kicked rotor, in particular the phenomenon of quantum anti-resonance. © 2023, CC BY-NC-SA.

关键词： Dynamics

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quantum recurrences in the kicked top

引用

Physical Review Research 2024年第2期6卷 023120-023120页

作者： Amit Anand Jack Davis Shohini Ghose Institute for Quantum Computing University of Waterloo Waterloo Ontario Canada N2L 3G1 Department of Physics and Astronomy University of Waterloo Waterloo Ontario Canada N2L 3G1 DIENS École Normale Supérieure PSL University CNRS INRIA 45 rue d'Ulm Paris 75005 France Department of Physics and Computer Science Wilfrid Laurier University Waterloo Ontario Canada N2L 3C5 Perimeter Institute for Theoretical Physics 31 Caroline St N Waterloo Ontario Canada N2L 2Y5

The emergence of classical chaos from an underlying quantum mechanics remains a challenging question due to the differences between dynamics driven by Schrödinger's equation versus Newton's equations. We present an infinite family of purely quantum recurrences that are not present in the classical limit of a chaotic system. They take the form of stroboscopic unitary evolutions in the quantum kicked top that act as the identity after a finite number of kicks. These state-independent recurrences are present in all finite dimensions and depend on the strength of the chaoticity parameter of the top. We further discuss the relationship of these periodicities to the quantum kicked rotor dynamics and the phenomenon of quantum antiresonance.

关键词： Chaos quantum chaos quantum correlations in quantum information quantum foundations quantum information theory quantum-to-classical transition

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Pretty good measurement for bosonic Gaussian ensembles

arXiv

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arXiv 2023年

作者： Mishra, Hemant K. Lami, Ludovico Mandayam, Prabha Wilde, Mark M. School of Electrical and Computer Engineering Cornell University IthacaNY14850 United States Hearne Institute for Theoretical Physics Department of Physics and Astronomy Center for Computation and Technology Louisiana State University Baton RougeLA70803 United States Institute of Theoretical Physics and IQST Universität Ulm Albert-Einstein-Allee Ulm11D-89069 Germany QuSoft Science Park 123 Amsterdam1098 XG Netherlands Korteweg–de Vries Institute for Mathematics University of Amsterdam Science Park 105-107 Amsterdam1098 XG Netherlands Institute for Theoretical Physics University of Amsterdam Science Park 904 Amsterdam1098 XH Netherlands Center for Quantum Information Communication and Computing IIT Madras Chennai600036 India Department of Physics Indian Institute of Technology Madras Chennai600036 India

The pretty good measurement is a fundamental analytical tool in quantum information theory, giving a method for inferring the classical label that identifies a quantum state chosen probabilistically from an ensemble. Identifying and constructing the pretty good measurement for the class of bosonic Gaussian states is of immediate practical relevance in quantum information processing tasks. Holevo recently showed that the pretty good measurement for a bosonic Gaussian ensemble is a bosonic Gaussian measurement that attains the accessible information of the ensemble [IEEE Trans. Inf. theory, 66(9):5634–564, 2020]. In this paper, we provide an alternate proof of Gaussianity of the pretty good measurement for a Gaussian ensemble of multimode bosonic states, with a focus on establishing an explicit and efficiently computable Gaussian description of the measurement. We also compute an explicit form of the mean square error of the pretty good measurement, which is relevant when using it for parameter estimation. Generalizing the pretty good measurement is a quantum instrument, called the pretty good instrument. We prove that the post-measurement state of the pretty good instrument is a faithful Gaussian state if the input state is a faithful Gaussian state whose covariance matrix satisfies a certain condition. Combined with our previous finding for the pretty good measurement and provided that the same condition holds, it follows that the expected output state is a faithful Gaussian state as well. In this case, we compute an explicit Gaussian description of the post-measurement and expected output states. Our findings imply that the pretty good instrument for bosonic Gaussian ensembles is no longer merely an analytical tool, but that it can also be implemented experimentally in quantum optics laboratories. Copyright © 2023, The Authors. All rights reserved.

关键词： Mean square error

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Nonequilibrium steady state phases of the interacting Aubry-André-Harper model

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Physical Review B 2020年第19期102卷 195142-195142页

作者： Yongchan Yoo Junhyun Lee Brian Swingle Department of Physics Condensed Matter Theory Center and Joint Quantum Institute University of Maryland College Park Maryland 20742 USA Department of Physics Condensed Matter Theory Center Maryland Center for Fundamental Physics and Joint Center for Quantum Information and Computer Science University of Maryland College Park Maryland 20742 USA

Here, we study the phase diagram of the Aubry-André-Harper model in the presence of strong interactions as the strength of the quasiperiodic potential is varied. Previous work has established the existence of a many-body localized phase at a large potential strength; here, we find a rich phase diagram in the delocalized regime characterized by spin transport and unusual correlations. We calculate the nonequilibrium steady states of a boundary-driven strongly interacting Aubry-André-Harper model by employing the time-evolving block decimation algorithm on matrix product density operators. From these steady states, we extract spin transport as a function of system size and quasiperiodic potential strength. These data show spin transport going from superdiffusive to subdiffusive well before the localization transition; comparing to previous results, we also find that the transport transition is distinct from a transition observed in the speed of operator growth in the model. We also investigate the correlation structure of the steady state and find an unusual oscillation pattern for intermediate values of the potential strength. The unusual spin transport and quantum correlation structure suggest multiple dynamical phases between the much-studied thermal and many-body localized phases.

关键词： Many-body localization quantum entanglement quantum transport 1-dimensional spin chains Tensor network methods

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