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arXiv 2025年

作者： Arora, Harsh Das, Bishal Kumar Suri, Baladitya Madhok, Vaibhav Centre for Nano Science and Engineering Indian Institute of Science Bengaluru560094 India Department of Physics Indian Institute of Technology Madras Chennai600036 India Center for Quantum Information Communication and Computing Indian Institute of Technology Madras Chennai600036 India Instrumentation and Applied Physics Indian Institute of Science Bengaluru560094 India

We present a new formulation for the emergence of classical dynamics in a quantum world by considering a path integral approach that also incorporates continuous measurements. Our program is conceptually different from the decoherence program as well as the quantum-to-classical transition framework with coarse-grained measurements. The path-integral formulation provides the joint statistics of a sequence of measurements with each Feynman path picking up an additional random phase due to measurements. The magnitude of this phase is proportional to the measurement strength, and we give conditions under which the dominant contribution to the probability amplitude comes from the trajectories in the vicinity of the classical paths. The proliferation of this information accross the environment, an essential feature of quantum Darwinism, takes place via scattering of plane-wave probes by the system. Extending to repeated measurements, we show that in the continuous limit, each system trajectory picks up an additional phase due to the momentum kicks from the probes - origin of the back-action force. We provide conditions for which the measurement provides sufficient "which-path" information and keeps the wave packet sufficiently localized. This allows for description of quantum-to-classical transition at the level of individual trajectories in contrast to the statistical ensemble interpretation provided by density matrices in the decoherence program. Copyright © 2025, The Authors. All rights reserved.

关键词： Integral equations

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Ultrabright Multiplexed Energy-Time-Entangled Photon Generation from Lithium Niobate on Insulator Chip

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Physical Review Applied 2021年第6期15卷 064059-064059页

作者： Guang-Tai Xue Yun-Fei Niu Xiaoyue Liu Jia-Chen Duan Wenjun Chen Ying Pan Kunpeng Jia Xiaohan Wang Hua-Ying Liu Yong Zhang Ping Xu Gang Zhao Xinlun Cai Yan-Xiao Gong Xiaopeng Hu Zhenda Xie Shining Zhu National Laboratory of Solid State Microstructures School of Physics School of Electronic Science and Engineering College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China State Key Laboratory of Optoelectronic Materials and Technologies and School of Physics and Engineering Sun Yat-sen University Guangzhou 510275 China Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computing National University of Defense Technology Changsha 410073 China

A high-flux entangled-photon source is a key resource for quantum optical study and application. Here, it is realized in a lithium niobate on isolator (LNOI) chip, with 2.79 × 1011 Hz/mW photon-pair rate and 1.53 × 109 Hz/(nm mW) spectral brightness. These data are boosted by over 2 orders of magnitude compared with existing technologies. A 160-nm-broad bandwidth is engineered for eight-channel multiplexed energy-time entanglement. Harnessed by high-extinction-frequency correlation and Franson interferences up to 99.17% visibility, such energy-time-entanglement multiplexing further enhances the high-flux data rate and warrants broad application in quantum-information processing on a chip.

关键词： Integrated optics Optical quantum information processing Optoelectronics Photon pairs & parametric down-conversion quantum state engineering Second order nonlinear optical processes Optical sources & detectors Waveguides

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quantum Optimization of Maximum Independent Set using Rydberg Atom Arrays

arXiv

引用

arXiv 2022年

作者： Ebadi, Sepehr Keesling, A. Cain, M. Wang, T.T. Levine, H. Bluvstein, D. Semeghini, G. Omran, A. Liu, J.-G. Samajdar, R. Luo, X.-Z. Nash, B. Gao, X. Barak, B. Farhi, E. Sachdev, S. Gemelke, N. Zhou, L. Choi, S. Pichler, H. Wang, S.-T. Greiner, M. Vuletić, V. Lukin, M.D. Department of Physics Harvard University CambridgeMA02138 United States QuEra Computing Inc. BostonMA02135 United States Department of Physics and Astronomy University of Waterloo WaterlooN2L 3G1 Canada Perimeter Institute for Theoretical Physics WaterlooONN2L 2Y5 Canada School of Engineering and Applied Science Harvard University CambridgeMA02138 United States Google Quantum AI VeniceCA90291 United States Center for Theoretical Physics Massachusetts Institute of Technology CambridgeMA02139 United States School of Natural Sciences Institute for Advanced Study PrincetonNJ08540 United States Walter Burke Institute for Theoretical Physics California Institute of Technology PasadenaCA91125 United States Institute for Theoretical Physics University of Innsbruck InnsbruckA-6020 Austria Institute for Quantum Optics and Quantum Information Austrian Academy of Sciences InnsbruckA-6020 Austria Department of Physics and Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States AWS Center for Quantum Computing PasadenaCA91125 United States

Realizing quantum speedup for practically relevant, computationally hard problems is a central challenge in quantum information science. Using Rydberg atom arrays with up to 289 qubits in two spatial dimensions, we experimentally investigate quantum algorithms for solving the Maximum Independent Set problem. We use a hardware-efficient encoding associated with Rydberg blockade, realize closed-loop optimization to test several variational algorithms, and subsequently apply them to systematically explore a class of graphs with programmable connectivity. We find the problem hardness is controlled by the solution degeneracy and number of local minima, and experimentally benchmark the quantum algorithm’s performance against classical simulated annealing. On the hardest graphs, we observe a superlinear quantum speedup in finding exact solutions in the deep circuit regime and analyze its origins. Copyright © 2022, The Authors. All rights reserved.

关键词： Benchmarking

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Device-Independent-quantum-randomness-enhanced zero-knowledge proof

arXiv

引用

arXiv 2021年

作者： Li, Cheng-Long Zhang, Kai-Yi Zhang, Xingjian Yang, Kui-Xing Han, Yu Cheng, Su-Yi Cui, Hongrui Liu, Wen-Zhao Li, Ming-Han Liu, Yang Bai, Bing Dong, Hai-Hao Zhang, Jun Ma, Xiongfeng Yu, Yu Fan, Jingyun Zhang, Qiang Pan, Jian-Wei Hefei National Laboratory for Physical Sciences at Microscale Department of Modern Physics University of Science and Technology of China Hefei230026 China Shanghai Branch CAS Center for Excellence Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai201315 China Shanghai Research Center for Quantum Sciences Shanghai201315 China Shanghai Jiao Tong University Shanghai200240 China Center for Quantum Information Institute for Interdisciplinary Information Sciences Tsinghua University Beijing100084 China Shenzhen Institute for Quantum Science and Engineering Department of Physics Southern University of Science and Technology Shenzhen518055 China State Key Laboratory of Mathematical Engineering and Advanced Computing Henan Zhengzhou450001 China Jinan Institute of Quantum Technology Jinan250101 China

Zero-knowledge proof (ZKP) is a fundamental cryptographic primitive that allows a prover to convince a verifier of the validity of a statement without leaking any further information[1]. As an efficient variant of ZKP, non-interactive zero-knowledge proof (NIZKP) adopting the Fiat-Shamir heuristic is essential to a wide spectrum of applications, such as federated learning[2], blockchain and social networks[3]. However, the heuristic is typically built upon the random oracle model making ideal assumptions about hash functions, which does not hold in reality and thus undermines the security of the protocol[4]. Here, we present a quantum resolution to the problem. Instead of resorting to a random oracle model, we implement a quantum randomness service. This service generates random numbers certified by the loophole-free Bell test[5, 6] and delivers them with post-quantum cryptography (PQC) authentication[7]. Employing this service, we conceive and implement a NIZKP of the three-colouring problem[8]. By bridging together three prominent research themes, quantum non-locality, PQC and ZKP, we anticipate this work to open a new paradigm of quantum information science. Copyright © 2021, The Authors. All rights reserved.

关键词： Hash functions

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One-step implementation of Rydberg nonadiabatic noncyclic geometric quantum computation in decoherence-free subspaces

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Physical Review A 2022年第6期105卷 062602-062602页

作者： Li-Na Sun F.-Q. Guo Zheng Shan M. Feng L.-L. Yan Shi-Lei Su School of Physics and Microelectronics Key Laboratory of Materials Physics of Ministry of Education Zhengzhou University Zhengzhou 450001 China State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou 450001 China State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy of Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 China Department of Physics Zhejiang Normal University Jinhua 321004 China Research Center for Quantum Precision Measurement Guangzhou Institute of Industry Technology Guangzhou 511458 China

quantum gates constructed by geometric phase are naturally robust to control errors due to the global nature of the geometric evolution path. Therefore, how to cope with the inevitable decoherence errors is worthy of serious attention for geometric quantum computation. Different from conventional nonadiabatic geometric quantum computation (NGQC), which needs the same evolution time for any geometric rotation angle, we have proposed and experimentally demonstrated nonadiabatic noncyclic geometric quantum computation (NNGQC) without the requirement of the cyclic evolution condition, which thus reduces decoherence errors due to shortened evolution time [J. W. Zhang et al., Phys. Rev. Lett. 127, 030502 (2021)]. In addition, the use of decoherence-free subspaces (DFS) is another effective strategy to protect quantum gates from dephasing error and has been studied in nonadiabatic holonomic quantum computation [G. F. Xu et al., Phys. Rev. Lett. 109, 170501 (2012)]. Motivated by previous studies, we propose a one-step scheme to implement single-qubit NNGQC operation in DFS constructed by two Rydberg atoms, and then generalize the scheme to the two-logical-qubit case in one step. The numerical results show that our scheme is robust against decoherence in contrast to the NGQC counterparts. The present scheme combines the features of NNGQC and DFS and can further reduce the impact of decoherence on gate infidelity, which may provide an option for the realization of Rydberg-atom-based quantum computation in the future.

关键词： Geometric & topological phases quantum gates Rydberg atoms & molecules

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

arXiv

引用

arXiv 2024年

作者： Tsemo, Peniel Bertrand Jayashankar, Akshaya Sugisaki, K. Baskaran, Nishanth Chakraborty, Sayan Prasannaa, V.S. Centre for Quantum Engineering Research and Education TCG CREST Sector V Salt Lake Kolkata700091 India Graduate School of Science and Technology Keio University 7-1 Shinkawasaki Saiwai-ku Kanagawa Kawasaki212-0032 Japan Quantum Computing Center Keio University 3-14-1 Hiyoshi Kohoku-ku Kanagawa Yokohama223-8522 Japan Keio University 2-15-45 Mita Minato-ku Tokyo108-8345 Japan Department of Electrical and Computer Engineering The University of British Columbia VancouverBCV6T 1Z4 Canada Institute for Advancing Intelligence TCG CREST Sector V Salt Lake Kolkata700091 India Ghaziabad201002 India

Although the Harrow-Hassidim-Lloyd (HHL) algorithm offers an exponential speedup in system size for treating linear equations of the form A→x =⃗b 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 post-selection-improved HHL (Psi-HHL) approach that involves a simple yet effective modification of the HHL algorithm to extract a feature of |x〉, and which leads to achieving optimal behaviour in κ (linear scaling) for large condition number situations. This has the important practical implication of having to use substantially fewer shots relative to the traditional HHL algorithm. Additionally, we discuss the capability of Psi-HHL to address the cases where A is singular. We carry out two sets of simulations, 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 million, 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. Although the feature of |x〉 considered in our examples is an overlap between the input and output states of the HHL algorithm, our approach is general and can be applied in principle to any transition matrix element involving |x〉. © 2024, CC BY.

关键词： quantum computers

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Quantifying quantum Entanglement in Two-Qubit Mixed State from Connected Correlator

SSRN

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SSRN 2023年

作者： Guo, Xingyu Ma, Chen-Te Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum Matter South China Normal University Guangdong Guangzhou510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter Southern Nuclear Science Computing Center South China Normal University Guangdong Guangzhou510006 China Asia Pacific Center for Theoretical Physics Pohang University of Science and Technology Gyeongsangbuk-do Pohang37673 Korea Republic of School of Physics and Telecommunication Engineering South China Normal University Guangdong Guangzhou510006 China The Laboratory for Quantum Gravity and Strings Department of Mathematics and Applied Mathematics University of Cape Town Private Bag Rondebosch7700 South Africa

We quantify quantum Entanglement using a connected correlation matrix. Quantifying the degree of entanglement between particles requires entanglement measures. The connected correlation matrix is used to quantify quantum Entanglement, suggesting that it encompasses all necessary entanglement measures. Our study suggests starting with a three-qubit state and obtaining a mixed state by partial tracing over one qubit. By considering the connected correlation, we aim to eliminate the non-connected sector and capture all relevant entanglement degrees. We classify mixed states and demonstrate that separable states exhibit the lowest correlation within each classified class. We then show that the entanglement measure monotonically increases for the correlation measure. This suggests that the connected correlation effectively quantifies quantum Entanglement. We compare the results to the logarithmic negativity, another measure of entanglement. Our findings indicate that the negativity increases with the correlation measure, but it is not monotonic. Finally, we propose that interpreting quantum Entanglement from a local perspective is possible, considering that the observable is a vector with locality but violates freedom of choice. © 2023, The Authors. All rights reserved.

关键词： quantum entanglement

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quantum Electrodynamics in a Topological Waveguide

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Physical Review X 2021年第1期11卷 011015-011015页

作者： Eunjong Kim Xueyue Zhang Vinicius S. Ferreira Jash Banker Joseph K. Iverson Alp Sipahigil Miguel Bello Alejandro González-Tudela Mohammad Mirhosseini Oskar Painter Thomas J. Watson Sr. Laboratory of Applied Physics and Kavli Nanoscience Institute California Institute of Technology Pasadena California 91125 USA Institute for Quantum Information and Matter California Institute of Technology Pasadena California 91125 USA AWS Center for Quantum Computing Pasadena California 91125 USA Instituto de Ciencia de Materiales de Madrid CSIC Madrid 28049 Spain Instituto de Física Fundamental IFF-CSIC Calle Serrano 113b Madrid 28006 Spain Gordon and Betty Moore Laboratory of Engineering California Institute of Technology Pasadena California 91125 USA

While designing the energy-momentum relation of photons is key to many linear, nonlinear, and quantum optical phenomena, a new set of light-matter properties may be realized by employing the topology of the photonic bath itself. In this work we experimentally investigate the properties of superconducting qubits coupled to a metamaterial waveguide based on a photonic analog of the Su-Schrieffer-Heeger model. We explore topologically induced properties of qubits coupled to such a waveguide, ranging from the formation of directional qubit-photon bound states to topology-dependent cooperative radiation effects. Addition of qubits to this waveguide system also enables direct quantum control over topological edge states that form in finite waveguide systems, useful for instance in constructing a topologically protected quantum communication channel. More broadly, our work demonstrates the opportunity that topological waveguide-QED systems offer in the synthesis and study of many-body states with exotic long-range quantum correlations.

关键词： Cavity quantum electrodynamics Metamaterials quantum description of light-matter interaction quantum optics with artificial atoms quantum simulation Superconducting quantum optics Symmetry protected topological states Topological effects in photonic systems

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Capacity approaching coding for low noise interactive quantum communication part I: Large alphabets

arXiv

引用

arXiv 2020年

作者： Leung, Debbie Nayak, Ashwin Shayeghi, Ala Touchette, Dave Yao, Penghui Yu, Nengkun Department of Combinatorics and Optimization Institute for Quantum Computing University of Waterloo and Perimeter Institute Department of Combinatorics and Optimization Institute for Quantum Computing University of Waterloo Department of Computer Science Institut Quantique Université de Sherbrooke Institute for Quantum Computing University of Waterloo Perimeter Institute State Key Laboratory for Novel Software Technology Nanjing University Centre for Quantum Software and Information Faculty of Engineering and Information Technology University of Technology Sydney

We consider the problem of implementing two-party interactive quantum communication over noisy channels, a necessary endeavor if we wish to fully reap quantum advantages for communication. For an arbitrary protocol with n messages, designed for a noiseless qudit channel over a poly (n) size alphabet, our main result is a simulation method that fails with probability less than 2-θ(n∈) and uses a qudit channel over the same alphabet n(1 + θ(√∈)) times, of which an ∈ fraction can be corrupted adversarially. The simulation is thus capacity achieving to leading order, and we conjecture that it is optimal up to a constant factor in the √ ∈ term. Furthermore, the simulation is in a model that does not require pre-shared resources such as randomness or entanglement between the communicating parties. Our work improves over the best previously known quantum result where the overhead is a non-explicit large constant [Brassard et al., FOCS'14] for low ∈. Copyright © 2020, The Authors. All rights reserved.

关键词： quantum communication

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Acceleration-Induced Effects in Stimulated Light-Matter Interactions

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Physical Review Letters 2022年第16期128卷 163603-163603页

作者： Barbara Šoda Vivishek Sudhir Achim Kempf Department of Physics University of Waterloo Waterloo Ontario N2L 3G1 Canada Perimeter Institute for Theoretical Physics Waterloo Ontario N2L 2Y5 Canada Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA LIGO Laboratory Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Applied Mathematics University of Waterloo Waterloo Ontario N2L 3G1 Canada Institute for Quantum Computing University of Waterloo Waterloo Ontario N2L 3G1 Canada

We show that, in addition to the Unruh effect, there exist two new phenomena that are due to acceleration in the quantum theory of the light-matter interaction. The first is the phenomenon of acceleration-induced transparency which arises since acceleration impacts not only the counter-rotating terms in the light-matter interaction (the cause of the conventional Unruh effect) but also the rotating wave terms. The second new phenomenon is that the Unruh effect can be stimulated, a phenomenon that arises since not only rotating-wave terms can be stimulated (as in conventional stimulated emission) but also counter-rotating terms. The new phenomena are potentially strong enough to be experimentally observable.

关键词： quantum description of light-matter interaction Relativistic & quantum electrodynamic effects in atoms, molecules,& ions Spontaneous emission Unruh effect

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