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arXiv 2019年

作者： Wu, Bujiao Cheng, Bin Zhang, Jialin Yung, Man-Hong Sun, Xiaoming Institute of Computing Technology Chinese Academy of Sciences Beijing China University of Chinese Academy of Sciences Beijing China Institute for Quantum Science and Engineering Department of Physics Southern University of Science and Technology Shenzhen518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China

Gaussian boson sampling is a promising model for demonstrating quantum computational supremacy, which eases the experimental challenge of the standard boson-sampling proposal. Here by analyzing the computational costs of classical simulation of Gaussian boson sampling, we establish a lower bound for achieving quantum computational supremacy for a class of Gaussian boson-sampling problems, where squeezed states are injected into every input mode. Specifically, we propose a method for simplifying the brute-force calculations for the transition probabilities in Gaussian boson sampling, leading to a significant reduction of the simulation costs. Particularly, our numerical results indicate that we can simulate 18 photons Gaussian boson sampling at the output subspace on a normal laptop, 20 photons on a commercial workstation with 256 cores, and suggest about 30 photons for supercomputers. These numbers are significantly smaller than those in standard boson sampling, suggesting Gaussian boson sampling may be more feasible for demonstrating quantum computational supremacy. Copyright © 2019, The Authors. All rights reserved.

关键词： Gaussian distribution

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Supervised learning in Hamiltonian reconstruction from local measurements on eigenstates

arXiv

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arXiv 2020年

作者： Cao, Chenfeng Hou, Shi-Yao Cao, Ningping Zeng, Bei Department Of Physics The Hong Kong University Of Science And Technology Clear Water Bay Kowloon Hong Kong College Of Physics And Electronic Engineering Center For Computational Sciences Sichuan Normal University Chengdu610068 China Department Of Mathematics & Statistics University Of Guelph GuelphON Canada Institute For Quantum Computing University Of Waterloo WaterlooON Canada

Reconstructing a system Hamiltonian through measurements on its eigenstates is an important inverse problem in quantum physics. Recently, it was shown that generic many-body local Hamiltonians can be recovered by local measurements without knowing the values of the correlation functions. In this work, we discuss this problem in more depth for different systems and apply the supervised learning method via neural networks to solve it. For low-lying eigenstates, the inverse problem is well-posed, neural networks turn out to be efficient and scalable even with a shallow network and a small data set. For middle-lying eigenstates, the problem is ill-posed, we present a modified method based on transfer learning accordingly. Neural networks can also efficiently generate appropriate initial points for numerical optimization based on the BFGS method. Copyright © 2020, The Authors. All rights reserved.

关键词： Hamiltonians

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Experimental Self-Characterization of quantum Measurements

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Physical Review Letters 2020年第4期124卷 040402-040402页

作者： Aonan Zhang Jie Xie Huichao Xu Kaimin Zheng Han Zhang Yiu-Tung Poon Vlatko Vedral Lijian Zhang National Laboratory of Solid State Microstructures Key Laboratory of Intelligent Optical Sensing and Manipulation (Ministry of Education) College of Engineering and Applied Sciences and School of Physics Nanjing University Nanjing 210093 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China Department of Mathematics Iowa State University Ames Iowa 50011 USA Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen 518055 China Atomic and Laser Physics Clarendon Laboratory University of Oxford Parks Road Oxford OX13PU United Kingdom Centre for Quantum Technologies National University of Singapore 3 Science Drive 2 117543 Singapore

The accurate and reliable description of measurement devices is a central problem in both observing uniquely nonclassical behaviors and realizing quantum technologies from powerful computing to precision metrology. To date quantum tomography is the prevalent tool to characterize quantum detectors. However, such a characterization relies on accurately characterized probe states, rendering reliability of the characterization lost in circular argument. Here we report a self-characterization method of quantum measurements based on reconstructing the response range—the entirety of attainable measurement outcomes, eliminating the reliance on known states. We characterize two representative measurements implemented with photonic setups and obtain fidelities above 99.99% with the conventional tomographic reconstructions. This initiates range-based techniques in characterizing quantum systems and foreshadows novel device-independent protocols of quantum information applications.

关键词： quantum information processing quantum measurements quantum optics quantum tomography

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quantum neural networks with data re-uploading for urban traffic time series forecasting

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Scientific Reports 2025年第1期15卷 1-21页

作者： Schetakis, Nikolaos Bonfini, Paolo Alisoltani, Negin Blazakis, Konstantinos Tsintzos, Symeon I. Askitopoulos, Alexis Aghamalyan, Davit Fafoutellis, Panagiotis Vlahogianni, Eleni I. Computational Mechanics and Optimization Laboratory School of Production Engineering and Management Technical University of Crete Chania 73100 Greece Quantum Innovation Pc Chania 73100 Greece Alma-Sistemi Srl Guidonia 00012 Italy Univ Gustave Eiffel COSYS GRETTIA Paris F-77454 France Department of Electrical and Computer Engineering Hellenic Mediterranean University Heraklion 71410 Greece QUBITECH Pc Athens 15231 Greece Institute of High Performance Computing A*STAR (Agency for Science Technology and Research) 1 Fusionopolis Way #16-16 Connexis Singapore 138632 Singapore Department of Transportation Planning and Engineering School of Civil Engineering National Technical University of Athens 5 Iroon Polytechniou Str Zografou Campus Athens 157 73 Greece

Accurate traffic forecasting plays a crucial role in modern Intelligent Transportation Systems (ITS), as it enables real-time traffic flow management, reduces congestion, and improves the overall efficiency of urban transportation networks. With the rise of quantum Machine Learning (QML), it has emerged a new paradigm possessing the potential to enhance predictive capabilities beyond what classical machine learning models can achieve. In the present work we pursue a heuristic approach to explore the potential of QML, and focus on a specific transport issue. In particular, as a case study we investigate a traffic forecast task for a major urban area in Athens (Greece), for which we possess high-resolution data. In this endeavor we explore the application of quantum Neural Networks (QNN), and, notably, we present the first application of quantum data re-uploading in the context of transport forecasting. This technique allows quantum models to better capture complex patterns, such as traffic dynamics, by repeatedly encoding classical data into a quantum state. Aside from providing a prediction model, we spend considerable effort in comparing the performance of our hybrid quantum-classical neural networks with classical deep learning approaches. We observe that, in fully connected network settings, hybrid quantum-classical models consistently underperform, with median scores approximately 10% worse than their purely classical counterparts across different configurations. In contrast, recursive architectures with data re-uploading show the opposite trend: hybrid models achieved up to 5% better median scores under comparable complexity settings. Additionally, these hybrid models converged in fewer training epochs, indicating improved training efficiency. Our results show that hybrid models achieve competitive accuracy with state-of-the-art classical methods, especially when the number of qubits and re-uploading blocks is increased. While the classical models demonstrate l

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Joint Measurement of the U235 Antineutrino Spectrum by PROSPECT and STEREO

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Physical Review Letters 2022年第8期128卷 081802-081802页

作者： H. Almazán M. Andriamirado A. B. Balantekin H. R. Band C. D. Bass D. E. Bergeron L. Bernard A. Blanchet A. Bonhomme N. S. Bowden C. D. Bryan C. Buck T. Classen A. J. Conant G. Deichert P. del Amo Sanchez A. Delgado M. V. Diwan M. J. Dolinski I. El Atmani A. Erickson B. T. Foust J. K. Gaison A. Galindo-Uribarri C. E. Gilbert S. Hans A. B. Hansell K. M. Heeger B. Heffron D. E. Jaffe S. Jayakumar X. Ji D. C. Jones J. Koblanski O. Kyzylova L. Labit J. Lamblin C. E. Lane T. J. Langford J. LaRosa A. Letourneau D. Lhuillier M. Licciardi M. Lindner B. R. Littlejohn X. Lu J. Maricic T. Materna M. P. Mendenhall A. M. Meyer R. Milincic P. E. Mueller H. P. Mumm J. Napolitano R. Neilson J. A. Nikkel S. Nour J. L. Palomino H. Pessard D. A. Pushin X. Qian J.-S. Réal J.-S. Ricol C. Roca R. Rogly R. Rosero T. Salagnac V. Savu S. Schoppmann M. Searles V. Sergeyeva T. Soldner A. Stutz P. T. Surukuchi M. A. Tyra R. L. Varner D. Venegas-Vargas M. Vialat P. B. Weatherly C. White J. Wilhelmi A. Woolverton M. Yeh C. Zhang X. Zhang Max-Planck-Institut für Kernphysik Saupfercheckweg 1 69117 Heidelberg Germany Department of Physics Illinois Institute of Technology Chicago Illinois USA Department of Physics University of Wisconsin Madison Wisconsin USA Wright Laboratory Department of Physics Yale University New Haven Connecticut USA Department of Physics Le Moyne College Syracuse New York USA National Institute of Standards and Technology Gaithersburg Maryland USA University Grenoble Alpes CNRS Grenoble INP LPSC-IN2P3 38000 Grenoble France IRFU CEA Université Paris-Saclay 91191 Gif-sur-Yvette France Nuclear and Chemical Sciences Division Lawrence Livermore National Laboratory Livermore California USA High Flux Isotope Reactor Oak Ridge National Laboratory Oak Ridge Tennessee USA Univ. Savoie Mont Blanc CNRS LAPP-IN2P3 74000 Annecy France Physics Division Oak Ridge National Laboratory Oak Ridge Tennessee USA Department of Physics and Astronomy University of Tennessee Knoxville Tennessee USA Brookhaven National Laboratory Upton New York USA Department of Physics Drexel University Philadelphia Pennsylvania USA George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta Georgia USA Department of Physics Temple University Philadelphia Pennsylvania USA Department of Physics and Astronomy University of Hawaii Honolulu Hawaii USA Institute for Quantum Computing and Department of Physics and Astronomy University of Waterloo Waterloo Ontario Canada Institut Laue-Langevin CS 20156 38042 Grenoble Cedex 9 France

The PROSPECT and STEREO collaborations present a combined measurement of the pure U235 antineutrino spectrum, without site specific corrections or detector-dependent effects. The spectral measurements of the two highest precision experiments at research reactors are found to be compatible with χ2/ndf=24.1/21, allowing a joint unfolding of the prompt energy measurements into antineutrino energy. This ν¯e energy spectrum is provided to the community, and an excess of events relative to the Huber model is found in the 5–6 MeV region. When a Gaussian bump is fitted to the excess, the data-model χ2 value is improved, corresponding to a 2.4σ significance.

关键词： Fission Neutrino interactions Nuclear reactors Neutrinos Neutrino detectors Scintillators

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Reduction theorem for secrecy over linear network code for active attacks

arXiv

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arXiv 2020年

作者： Hayashi, Masahito Owari, Masaki Kato, Go Cai, Ning Graduate School of Mathematics Nagoya University Nagoya464-8602 Japan Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518000 China Centre for Quantum Technologies National University of Singapore 3 Science Drive 2 117542 Singapore Department of Computer Science Faculty of Informatics Shizuoka University Japan NTT Communication Science Laboratories NTT Corporation Japan School of Information Science and Technology ShanghaiTech University Middle Huaxia Road no 393 Pudong Shanghai201210 China

We discuss the effect of sequential error injection on information leakage under a network code. We formulate a network code for the single transmission setting and the multiple transmission setting. Under this formulation, we show that the eavesdropper cannot improve the power of eavesdropping by sequential error injection when the operations in the network are linear *** demonstrate the usefulness of this reduction theorem by applying a concrete example of network. Copyright © 2020, The Authors. All rights reserved.

关键词： Network coding

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Observation of Three-Photon Spontaneous Parametric Down-Conversion in a Superconducting Parametric Cavity

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Physical Review X 2020年第1期10卷 011011-011011页

作者： C. W. Sandbo Chang Carlos Sabín P. Forn-Díaz Fernando Quijandría A. M. Vadiraj I. Nsanzineza G. Johansson C. M. Wilson Institute for Quantum Computing and Electrical and Computer Engineering University of Waterloo Waterloo Ontario N2L 3G1 Canada Instituto de Física Fundamental CSIC Serrano 113-bis 28006 Madrid Spain Institut de Física d’Altes Energies (IFAE) The Barcelona Institute of Science and Technology (BIST) Bellaterra (Barcelona) 08193 Spain Barcelona Supercomputing Center-CNS Barcelona 08034 Spain Microtechnology and Nanoscience MC2 Chalmers University of Technology SE-412 96 Göteborg Sweden

Spontaneous parametric down-conversion (SPDC) has been a key enabling technology in exploring quantum phenomena and their applications for decades. For instance, traditional SPDC, which splits a high-energy pump photon into two lower-energy photons, is a common way to produce entangled photon pairs. Since the early realizations of SPDC, researchers have thought to generalize it to higher order, e.g., to produce entangled photon triplets. However, directly generating photon triplets through a single SPDC process has remained elusive. Here, using a flux-pumped superconducting parametric cavity, we demonstrate direct three-photon SPDC, with photon triplets generated in a single cavity mode or split between multiple modes. With strong pumping, the states can be quite bright, with flux densities exceeding 60 photons per second per hertz. The observed states are strongly non-Gaussian, which has important implications for potential applications. In the single-mode case, we observe a triangular star-shaped distribution of quadrature voltages, indicative of the long-predicted “star state.” The observed state shows strong third-order correlations, as expected for a state generated by a cubic Hamiltonian. By pumping at the sum frequency of multiple modes, we observe strong three-body correlations between multiple modes, strikingly, in the absence of second-order correlations. We further analyze the third-order correlations under mode transformations by the symplectic symmetry group, showing that the observed transformation properties serve to “fingerprint” the specific cubic Hamiltonian that generates them. The observed non-Gaussian, third-order correlations represent an important step forward in quantum optics and may have a strong impact on quantum communication with microwave fields as well as continuous-variable quantum computation.

关键词： quantum communication quantum computation quantum optics

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Driving-induced resonance narrowing in a strongly coupled cavity-qubit system

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Physical Review A 2020年第4期102卷 043716-043716页

作者： Eyal Buks Paul Brookes Eran Ginossar Chunqing Deng Jean-Luc F. X. Orgiazzi Martin Otto Adrian Lupascu Andrew and Erna Viterbi Department of Electrical Engineering Technion Haifa 32000 Israel Department of Physics and Astronomy University College London Gower Street London WC1E 6BT United Kingdom Advanced Technology Institute and Department of Physics University of Surrey Guildford GU2 7XH United Kingdom Institute for Quantum Computing University of Waterloo Waterloo Ontario Canada N2L 3G1

We study a system consisting of a superconducting flux qubit strongly coupled to a microwave cavity. Externally applied qubit driving is employed in order to manipulate the spectrum of dressed states. We observe resonance narrowing in the region where the splitting between the two dressed fundamental resonances is tuned to zero. The narrowing in this region of overlapping resonances can be exploited for long-time storage of quantum states. In addition, we measure the response to strong cavity mode driving, and find a qualitative deviation between the experimental results and the predictions of a semiclassical model. On the other hand, good agreement is obtained using theoretical predictions obtained by numerically integrating the master equation governing the system's dynamics. The observed response demonstrates a process of a coherent cancellation of two metastable dressed states.

关键词： quantum control

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Strong Coupling of Two Individually Controlled Atoms via a Nanophotonic Cavity

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Physical Review Letters 2020年第6期124卷 063602-063602页

作者： Polnop Samutpraphoot Tamara Đorđević Paloma L. Ocola Hannes Bernien Crystal Senko Vladan Vuletić Mikhail D. Lukin Department of Physics Harvard University Cambridge Massachusetts 02138 USA Pritzker School of Molecular Engineering University of Chicago Chicago Illinois 60637 USA Department of Physics and Astronomy University of Waterloo Waterloo Ontario N2L 3R1 Canada Institute for Quantum Computing University of Waterloo Waterloo Ontario N2L 3R1 Canada Department of Physics and Research Laboratory of Electronics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA

We demonstrate photon-mediated interactions between two individually trapped atoms coupled to a nanophotonic cavity. Specifically, we observe collective enhancement when the atoms are resonant with the cavity and level repulsion when the cavity is coupled to the atoms in the dispersive regime. Our approach makes use of individual control over the internal states of the atoms and their position with respect to the cavity mode, as well as the light shifts to tune atomic transitions individually, allowing us to directly observe the anticrossing of the bright and dark two-atom states. These observations open the door for realizing quantum networks and studying quantum many-body physics based on atom arrays coupled to nanophotonic devices.

关键词： Cavity quantum electrodynamics Collective effects in quantum optics Hybrid quantum systems quantum control quantum optics Superradiance & subradiance

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Enhancing the Harrow-Hassidim-Lloyd (HHL) algorithm in systems with large condition numbers

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Physical Review Research 2025年第2期7卷 023270-023270页

作者： Peniel Bertrand Tsemo Akshaya Jayashankar K. Sugisaki Nishanth Baskaran Sayan Chakraborty V. S. Prasannaa Centre for Quantum Engineering Research and Education TCG CREST Sector V Salt Lake Kolkata 700091 India Department of Physics IIT Tirupati Chindepalle Andhra Pradesh 517619 India Graduate School of Science and Technology Keio University 7-1 Shinkawasaki Saiwai-ku Kawasaki Kanagawa 212-0032 Japan Quantum Computing Center Keio University 3-14-1 Hiyoshi Kohoku-ku Yokohama Kanagawa 223-8522 Japan Keio University Sustainable Quantum Artificial Intelligence Center (KSQAIC) Keio University 2-15-45 Mita Minato-ku Tokyo 108-8345 Japan Department of Electrical and Computer Engineering The University of British Columbia Vancouver British Columbia V6T 1Z4 Canada Institute for Advancing Intelligence TCG CREST Sector V Salt Lake Kolkata 700091 India Academy of Scientific and Innovative Research (AcSIR) Ghaziabad 201002 India

Although the Harrow-Hassidim-Lloyd (HHL) algorithm offers an exponential speedup in system size for treating linear equations of the form Ax⃗=b⃗ on quantum computers when compared to their traditional counterparts, it faces a challenge related to the condition number (κ) scaling of the A matrix. In this work, we address the issue by introducing the postselection-improved HHL (Psi-HHL) framework that operates on a simple yet effective premise: subtracting mixed and wrong signals to extract correct signals while providing the benefit of optimal scaling in the condition number of A (denoted as κ) for large κ scenarios. This approach, which leads to minimal increase in circuit depth, has the important practical implication of having to use substantially fewer shots relative to the traditional HHL algorithm. The term “signal” refers to a feature of |x〉. We design circuits for overlap and expectation value estimation in the Psi-HHL framework. We demonstrate performance of Psi-HHL via numerical simulations. We carry out two sets of computations, where we go up to 26-qubit calculations, to demonstrate the ability of Psi-HHL to handle situations involving large-κ matrices via (a) a set of toy matrices, for which we go up to size 64×64 and κ values of up to ≈1×106, and (b) application to quantum chemistry, where we consider matrices up to size 256×256 that reach κ of about 393. The molecular systems that we consider are Li2, KH, RbH, and CsH.

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