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arXiv 2020年

作者： Gosset, David Grier, Daniel Kerzner, Alex Schaeffer, Luke Institute for Quantum Computing University of Waterloo Canada Department of Combinatorics and Optimization University of Waterloo Canada Perimeter Institute for Theoretical Physics Waterloo Canada Cheriton School of Computer Science University of Waterloo Canada Department of Computer Science and Engineering Department of Mathematics University of California San Diego United States Joint Center for Quantum Information and Computer Science College ParkMD United States

A general quantum circuit can be simulated classically in exponential time. If it has a planar layout, then a tensor-network contraction algorithm due to Markov and Shi has a runtime exponential in the square root of its size, or more generally exponential in the treewidth of the underlying graph. Separately, Gottesman and Knill showed that if all gates are restricted to be Clifford, then there is a polynomial time simulation. We combine these two ideas and show that treewidth and planarity can be exploited to improve Clifford circuit simulation. Our main result is a classical algorithm with runtime scaling asymptotically as nω/2 1.19 which samples from the output distribution obtained by measuring all n qubits of a planar graph state in given Pauli bases. Here ω is the matrix multiplication exponent. We also provide a classical algorithm with the same asymptotic runtime which samples from the output distribution of any constant-depth Clifford circuit in a planar geometry. Our work improves known classical algorithms with cubic runtime. A key ingredient is a mapping which, given a tree decomposition of some graph G, produces a Clifford circuit with a structure that mirrors the tree decomposition and which emulates measurement of the corresponding graph state. We provide a classical simulation of this circuit with the runtime stated above for planar graphs and otherwise ntω−1 where t is the width of the tree decomposition. Our algorithm incorporates two subroutines which may be of independent interest. The first is a matrix-multiplication-time version of the Gottesman-Knill simulation of multi-qubit measurement on stabilizer states. The second is a new classical algorithm for solving symmetric linear systems over F2 in a planar geometry, extending previous works which only applied to non-singular linear systems in the analogous setting. © 2020, CC BY.

关键词： Timing circuits

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Electric-magnetic duality in twisted quantum double model of topological orders

arXiv

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arXiv 2020年

作者： Hu, Yuting Wan, Yidun Department of Physics Institute for Quantum Science and Engineering South University of Science and Technology Shenzhen518055 China State Key Laboratory of Surface Physics Fudan University Shanghai200433 China Department of Physics Center for Field Theory and Particle Physics Institute for Nanoelectronic devices and Quantum computing Fudan University Shanghai200433 China

We derive a partial electric-magnetic (PEM) duality transformation of the twisted quantum double (TQD) model TQD(G,α)—discrete Dijkgraaf-Witten model—with a finite gauge group G, which has an Abelian normal subgroup N, and a three-cocycle α ∈ H3(G,U(1)). Any equivalence between two TQD models, say, TQD(G,α) and TQD(G0,α0), can be realized as a PEM duality transformation, which exchanges the N-charges and N-fluxes only. Via the PEM duality, we construct an explicit isomorphism between the corresponding TQD algebras Dα(G) and Dα0(G0) and derive the map between the anyons of one model and those of the other. Copyright © 2020, The Authors. All rights reserved.

关键词： quantum theory

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Strong quantum nonlocality without entanglement in multipartite quantum systems

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Physical Review A 2020年第4期102卷 042228-042228页

作者： Pei Yuan Guojing Tian Xiaoming Sun CAS Key Laboratory of Network Data Science and Technology Institute of Computing Technology Chinese Academy of Sciences 100190 Beijing China School of Computer Science and Technology University of Chinese Academy of Sciences Beijing 100049 China CAS Center of Excellence in Topological Quantum Computation Beijing 100049 China

In this paper, we generalize the concept of strong quantum nonlocality from two aspects. First, in a tripartite quantum system, we present a construction of strongly nonlocal quantum states containing 6(d−1)2 orthogonal product states in Cd⊗Cd⊗Cd and build 6d2−8d+4 product states in Cd⊗Cd⊗Cd+1, which have been proved to be strongly nonlocal. Obviously, both results turn out to be one order of magnitude smaller than the number of basis states d3 for d≥3. Second, we give explicit forms of strongly nonlocal orthogonal product basis in C3⊗C3⊗C3⊗C3 and C4⊗C4⊗C4⊗C4 quantum systems, where four is the largest known number of subsystems in which there exists strong quantum nonlocality without entanglement up to now. All the results positively answer the open problems raised by Halder et al. [Phys. Rev. Lett. 122, 040403 (2019)]; that is, there do exist a small number of quantum states that can demonstrate strong quantum nonlocality without entanglement.

关键词： Nonlocality

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quantum speedup for track reconstruction in particle accelerators

arXiv

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arXiv 2021年

作者： Magano, Duarte Kumar, Akshat Kālis, Mārtiņš Locāns, Andris Glos, Adam Pratapsi, Sagar Quinta, Gonçalo Dimitrijevs, Maksims Rivošs, Aleksander Bargassa, Pedrame Seixas, João Ambainis, Andris Omar, Yasser Physics of Information and Quantum Technologies Group Instituto de Telecomunicações Portugal Instituto Superior Técnico Universidade de Lisboa Portugal Department of Mathematics Clarkson University United States Center for Quantum Computer Science Faculty of Computing University of Latvia Latvia Institute of Theoretical and Applied Informatics Polish Academy of Sciences Poland Portuguese Quantum Institute Portugal Laboratório de Instrumentação e Física Experimental de Partículas Portugal Center for Physics and Engineering of Advanced Materials Portugal

To investigate the fundamental nature of matter and its interactions, particles are accelerated to very high energies and collided inside detectors, producing a multitude of other particles that are scattered in all directions. As charged particles traverse the detector, they leave signals of their passage. The problem of track reconstruction is to recover the original trajectories from these signals. This challenging data analysis task will become even more demanding as the luminosity of future accelerators increases, leading to collision events with a more complex structure. We identify four fundamental routines present in every local tracking method and analyse how they scale in the context of a standard tracking algorithm. We show that for some of these routines we can reach a lower computational complexity with quantum search algorithms. Although the found quantum speedups are mild, this constitutes, to the best of our knowledge, the first rigorous evidence of a quantum advantage for a high-energy physics data processing task. Copyright © 2021, The Authors. All rights reserved.

关键词： Charged particles

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Deep neural network discrimination of multiplexed superconducting qubit states

arXiv

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arXiv 2021年

作者： Lienhard, Benjamin Vepsäläinen, Antti Govia, Luke C.G. Hoffer, Cole R. Qiu, Jack Y. Ristè, Diego Ware, Matthew Kim, David Winik, Roni Melville, Alexander Niedzielski, Bethany Yoder, Jonilyn Ribeill, Guilhem J. Ohki, Thomas A. Krovi, Hari K. Orlando, Terry P. Gustavsson, Simon Oliver, William D. Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States Quantum Engineering and Computing Group Raytheon BBN Technologies CambridgeMA02138 United States MIT Lincoln Laboratory LexingtonMA02421 United States

Demonstrating a quantum computational advantage will require high-fidelity control and readout of multi-qubit systems. As system size increases, multiplexed qubit readout becomes a practical necessity to limit the growth of resource overhead. Many contemporary qubit-state discriminators presume single-qubit operating conditions or require considerable computational effort, limiting their potential extensibility. Here, we present multi-qubit readout using neural networks as state discriminators. We compare our approach to contemporary methods employed on a quantum device with five superconducting qubits and frequency-multiplexed readout. We find that fully-connected feedforward neural networks increase the qubit-state-assignment fidelity for our system. Relative to contemporary discriminators, the assignment error rate is reduced by up to 25 % due to the compensation of system-dependent nonidealities such as readout crosstalk which is reduced by up to one order of magnitude. Our work demonstrates a potentially extensible building block for high-fidelity readout relevant to both near-term devices and future fault-tolerant systems. Copyright © 2021, The Authors. All rights reserved.

关键词： Deep neural networks

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Hard jet substructure in a multistage approach

引用

Physical Review C 2024年第4期110卷 044907页

作者： Y. Tachibana A. Kumar A. Majumder A. Angerami R. Arora S. A. Bass S. Cao Y. Chen T. Dai L. Du R. Ehlers H. Elfner W. Fan R. J. Fries C. Gale Y. He M. Heffernan U. Heinz B. V. Jacak P. M. Jacobs S. Jeon Y. Ji K. Kauder L. Kasper W. Ke M. Kelsey M. Kordell, II J. Latessa Y.-J. Lee D. Liyanage A. Lopez M. Luzum S. Mak A. Mankolli C. Martin H. Mehryar T. Mengel J. Mulligan C. Nattrass D. Oliinychenko J.-F. Paquet J. H. Putschke G. Roland B. Schenke L. Schwiebert A. Sengupta C. Shen A. Silva C. Sirimanna D. Soeder R. A. Soltz I. Soudi J. Staudenmaier M. Strickland J. Velkovska G. Vujanovic X.-N. Wang R. L. Wolpert W. Zhao Yuwa Akita-city 010-1292 Japan Department of Physics McGill University Montréal Québec H3A 2T8 Canada Department of Physics and Astronomy Wayne State University Detroit Michigan 48201 USA Department of Physics University of Regina Regina Saskatchewan S4S 0A2 Canada Lawrence Livermore National Laboratory Livermore California 94550 USA Research Computing Group University Technology Solutions The University of Texas at San Antonio San Antonio Texas 78249 USA Department of Physics Duke University Durham North Carolina 27708 USA Institute of Frontier and Interdisciplinary Science Shandong University Qingdao Shandong 266237 China Laboratory for Nuclear Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics and Astronomy Vanderbilt University Nashville Tennessee 37235 USA Department of Physics and Astronomy University of Tennessee Knoxville Tennessee 37996 USA Physics Division Oak Ridge National Laboratory Oak Ridge Tennessee 37830 USA Department of Physics University of California Berkeley California 94270 USA Nuclear Science Division Lawrence Berkeley National Laboratory Berkeley California 94270 USA GSI Helmholtzzentrum für Schwerionenforschung 64291 Darmstadt Germany Institute for Theoretical Physics Goethe University 60438 Frankfurt am Main Germany Frankfurt Institute for Advanced Studies 60438 Frankfurt am Main Germany Cyclotron Institute Texas A&M University College Station Texas 77843 USA Department of Physics and Astronomy Texas A&M University College Station Texas 77843 USA Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum Matter South China Normal University Guangzhou 510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter Southern Nuclear Science Computing Center South China Normal University Guangzhou 510006 China Department of Physics The Ohio Stat

We present predictions and postdictions for a wide variety of hard jet-substructure observables using a multistage model within the jetscape framework. The details of the multistage model and the various parameter choices are described in [Phys. Rev. C 107, 034911 (2023)]. A novel feature of this model is the presence of two stages of jet modification: a high-virtuality phase [modeled using the modular all twist transverse-scattering elastic-drag and radiation model (matter)], where modified coherence effects diminish medium-induced radiation, and a lower virtuality phase [modeled using the linear Boltzmann transport model (lbt)], where parton splits are fully resolved by the medium as they endure multiple scattering induced energy loss. Energy-loss calculations are carried out on event-by-event viscous fluid dynamic backgrounds constrained by experimental data. The uniform and consistent descriptions of multiple experimental observables demonstrate the essential role of modified coherence effects and the multistage modeling of jet evolution. Using the best choice of parameters from [Phys. Rev. C 107, 034911] (2023)], and with no further tuning, we present calculations for the medium modified jet fragmentation function, the groomed jet momentum fraction zg and angular separation rg distributions, as well as the nuclear modification factor of groomed jets. These calculations provide accurate descriptions of published data from experiments at the Large Hadron Collider. Furthermore, we provide predictions from the multistage model for future measurements at the BNL Relativistic Heavy Ion Collider.

关键词： Hard scattering Jet quenching Jets & heavy flavor physics Quark & gluon jets Quark-gluon plasma Relativistic heavy-ion collisions

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Detecting mixed-unitary quantum channels is NP-hard

arXiv

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arXiv 2019年

作者： Lee, Colin Do-Yan Watrous, John Institute for Quantum Computing School of Computer Science University of Waterloo Canada

A quantum channel is said to be a mixed-unitary channel if it can be expressed as a convex combination of unitary channels. We prove that, given the Choi representation of a quantum channel Φ, it is NP-hard with respect to polynomial-time Turing reductions to determine whether or not Φ is a mixed-unitary channel. This hardness result holds even under the assumption that Φ is not within an inverse-polynomial distance (in the dimension of the space upon which Φ acts) of the boundary of the mixed-unitary channels. Copyright © 2019, The Authors. All rights reserved.

关键词： Polynomial approximation

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Dynamic Asset Allocation with Expected Shortfall via quantum Annealing

arXiv

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arXiv 2021年

作者： Xu, Hanjing Dasgupta, Samudra Pothen, Alex Banerjee, Arnab Department of Computer Science Purdue University West LafayetteIN47906 United States Department of Physics Purdue University West LafayetteIN47906 United States Oak Ridge National Laboratory Quantum Computing Institute Oak RidgeTN37831 United States Bredesen Center University of Tennessee KnoxvilleTN37996 United States

Recent advances in quantum hardware offer new approaches to solve various optimization problems that can be computationally expensive when classical algorithms are employed. We propose a hybrid quantum-classical algorithm to solve a dynamic asset allocation problem where a target return and a target risk metric (expected shortfall) are specified. We propose an iterative algorithm that treats the target return as a constraint in a Markowitz portfolio optimization model, and dynamically adjusts the target return to satisfy the targeted expected shortfall. The Markowitz optimization is formulated as a Quadratic Unconstrained Binary Optimization (QUBO) problem. The use of the expected shortfall risk metric enables the modeling of extreme market events. We compare the results from D-Wave’s 2000Q and Advantage quantum annealers using real-world financial data. Both quantum annealers are able to generate portfolios with more than 80% of the return of the classical optimal solutions, while satisfying the expected shortfall. We observe that experiments on assets with higher correlations tend to perform better, which may help to design practical quantum applications in the near term. © 2021, CC BY.

关键词： Iterative methods

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Quingo: A programming framework for heterogeneous quantum-classical computing with NISQ features

arXiv

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arXiv 2020年

作者： Fu, Xiang Yu, Jintao Su, Xing Jiang, Hanru Wu, Hua Cheng, Fucheng Deng, Xi Zhang, Jinrong Jin, Lei Yang, Yihang Xu, Le Hu, Chunchao Huang, Anqi Huang, Guangyao Qiang, Xiaogang Deng, Mingtang Xu, Ping Xu, Weixia Liu, Wanwei Zhang, Yu Deng, Yuxin Wu, Junjie Feng, Yuan Institute for Quantum Information & State Key Laboratory of High Performance Computing College of Computer National University of Defense Technology Changsha410073 China State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou450001 China College of Computer National University of Defense Technology Changsha410073 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518055 China Shanghai Key Laboratory of Trustworthy Computing East China Normal University Shanghai200062 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518055 China School of Information Engineering Zhengzhou University Zhengzhou450001 China Institute for Quantum Information & State Key Laboratory of High Performance Computing College of Computer National University of Defense Technology Changsha410073 China Department of Computing Science College of Computer National University of Defense Technology Changsha410073 China School of Computer Science and Technology University of Science and Technology of China Hefei230027 China Shanghai Key Laboratory of Trustworthy Computing East China Normal University Shanghai200062 China Institute for Quantum Information & State Key Laboratory of High Performance Computing College of Computer National University of Defense Technology Changsha410073 China Centre for Quantum Software and Information University of Technology Sydney Sydney2007 Australia

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Fast estimation of outcome probabilities for quantum circuits

arXiv

引用

arXiv 2021年

作者： Pashayan, Hakop Reardon-Smith, Oliver Korzekwa, Kamil Bartlett, Stephen D. Institute for Quantum Computing Department of Combinatorics and Optimization University of Waterloo ONN2L 3G1 Canada Perimeter Institute for Theoretical Physics WaterlooONN2L 2Y5 Canada Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Kraków30-348 Poland Centre for Engineered Quantum Systems School of Physics The University of Sydney SydneyNSW2006 Australia

We present two classical algorithms for the simulation of universal quantum circuits on n qubits constructed from c instances of Clifford gates and t arbitrary-angle Z-rotation gates such as T gates. Our algorithms complement each other by performing best in different parameter regimes. The Estimate algorithm produces an additive precision estimate of the Born rule probability of a chosen measurement outcome with the only source of run-time inefficiency being a linear dependence on the stabilizer extent (which scales like ≈ 1.17t for T gates). Our algorithm is state-of-the-art for this task: as an example, in approximately 13 hours (on a standard desktop computer), we estimated the Born rule probability to within an additive error of 0.03, for a 50-qubit, 60 non-Clifford gate quantum circuit with more than 2000 Clifford gates. Our second algorithm, Compute, calculates the probability of a chosen measurement outcome to machine precision with run-time O (2t−rt) where r is an efficiently computable, circuit-specific quantity. With high probability, r is very close to min {t, n − w} for random circuits with many Clifford gates, where w is the number of measured qubits. Compute can be effective in surprisingly challenging parameter regimes, e.g., we can randomly sample Clifford+T circuits with n = 55, w = 5, c = 105 and t = 80 T gates, and then compute the Born rule probability with a run-time consistently less than 10 minutes using a single core of a standard desktop computer. We provide a C+Python implementation of our algorithms and benchmark them using random circuits, the hidden shift algorithm and the quantum approximate optimization algorithm (QAOA). Copyright © 2021, The Authors. All rights reserved.

关键词： Probability

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