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Flow of quantum correlations in noisy two-mode squeezed microwave states

Physical Review A 2022年第5期106卷 052415-052415页

作者： M. Renger S. Pogorzalek F. Fesquet K. Honasoge F. Kronowetter Q. Chen Y. Nojiri K. Inomata Y. Nakamura A. Marx F. Deppe R. Gross K. G. Fedorov Walther-Meißner-Institut Bayerische Akademie der Wissenschaften 85748 Garching Germany Physik-Department Technische Universität München 85748 Garching Germany Rohde & Schwarz GmbH & Co. KG Mühldorfstraße 15 81671 Munich Germany RIKEN Center for Quantum Computing (RQC) Wako Saitama 351-0198 Japan National Institute of Advanced Industrial Science and Technology 1-1-1 Umezono Tsukuba Ibaraki 305-8563 Japan Department of Applied Physics Graduate School of Engineering The University of Tokyo Bunkyo-ku Tokyo 113-8656 Japan Munich Center for Quantum Science and Technology (MCQST) Schellingstr. 4 80799 Munich Germany

We study nonclassical correlations in propagating two-mode squeezed microwave states in the presence of noise. We focus on two different types of correlations, namely, quantum entanglement and quantum discord. quantum discord has various intriguing fundamental properties which require experimental verification, such as the asymptotic robustness to environmental noise. Here, we experimentally investigate quantum discord in propagating two-mode squeezed microwave states generated via superconducting Josephson parametric amplifiers. By exploiting an asymmetric noise injection into these entangled states, we demonstrate the robustness of quantum discord against thermal noise while verifying the sudden death of entanglement. Furthermore, we investigate the difference between quantum discord and entanglement of formation, which can be directly related to the flow of locally inaccessible information between the environment and the bipartite subsystem. We observe a crossover behavior between quantum discord and entanglement for low noise photon numbers, which is a result of the tripartite nature of noise injection. We demonstrate that the difference between entanglement and quantum discord can be related to the security of certain quantum key distribution protocols.

关键词： quantum communication quantum correlations in quantum information quantum discord quantum entanglement

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quantum Coding with Low-Depth Random Circuits

引用

Physical Review X 2021年第3期11卷 031066-031066页

作者： Michael J. Gullans Stefan Krastanov David A. Huse Liang Jiang Steven T. Flammia Joint Center for Quantum Information and Computer Science NIST/University of Maryland College Park Maryland 20742 USA Department of Physics Princeton University Princeton New Jersey 08544 USA John A. Paulson School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Pritzker School of Molecular Engineering The University of Chicago Illinois 60637 USA AWS Center for Quantum Computing Pasadena California 91125 USA

Random quantum circuits have played a central role in establishing the computational advantages of near-term quantum computers over their conventional counterparts. Here, we use ensembles of low-depth random circuits with local connectivity in D≥1 spatial dimensions to generate quantum error-correcting codes. For random stabilizer codes and the erasure channel, we find strong evidence that a depth O(logN) random circuit is necessary and sufficient to converge (with high probability) to zero failure probability for any finite amount below the optimal erasure threshold, set by the channel capacity, for any D. Previous results on random circuits have only shown that O(N1/D) depth suffices or that O(log3N) depth suffices for all-to-all connectivity (D→∞). We then study the critical behavior of the erasure threshold in the so-called moderate deviation limit, where both the failure probability and the distance to the optimal threshold converge to zero with N. We find that the requisite depth scales like O(logN) only for dimensions D≥2 and that random circuits require O(N) depth for D=1. Finally, we introduce an “expurgation” algorithm that uses quantum measurements to remove logical operators that cause the code to fail by turning them into either additional stabilizers or into gauge operators in a subsystem code. With such targeted measurements, we can achieve sublogarithmic depth in D≥2 spatial dimensions below capacity without increasing the maximum weight of the check operators. We find that for any rate beneath the capacity, high-performing codes with thousands of logical qubits are achievable with depth 4–8 expurgated random circuits in D=2 dimensions. These results indicate that finite-rate quantum codes are practically relevant for near-term devices and may significantly reduce the resource requirements to achieve fault tolerance for near-term applications.

关键词： quantum channels quantum computation quantum error correction

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High performance reconciliation for practical quantum key distribution systems

arXiv

引用

arXiv 2021年

作者： Mao, Hao-Kun Li, Qiong Hao, Peng-Lei Abd-El-Atty, Bassem Iliyasu, Abdullah M. Department of Computer Science and Technology Harbin Institute of Technology Harbin150080 China 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 Computer Science Faculty of Computers and Information Luxor University Egypt School of Computing Tokyo Institute of Technology Yokohama226-8502 Japan Electrical Engineering Department College of Engineering Prince Sattam Bin Abdulaziz University Al-Kharj Al-Kharj Saudi Arabia School of Computer Science and Technology Changchun University of Science and Technology Changchun130022 China

quantum key distribution (QKD) is a promising technique for secure communication based on quantum mechanical principles. To improve the secure key rate of a QKD system, most studies on reconciliation primarily focused on improving the efficiency. With the increasing performance of QKD systems, the research priority has shifted to the improvement of both throughput and efficiency. In this paper, we propose a high performance solution of Cascade reconciliation, including a high-throughput-oriented framework and an integrated-optimization-oriented scheme. Benefiting from the fully utilizing computation and storage resources, effectively dealing with communication delays, the integrated-optimization-oriented parameters setting, etc., an excellent overall performance was achieved. Experimental results showed that, the throughput of up to 570Mbps with an efficiency of 1.038 was achieved, which, to our knowledge, was more than four times faster than any throughput previously demonstrated. Furthermore, throughputs on real data sets were capable of reaching up to 86Mbps even on embedded platforms. Additionally, our solution offers good adaptability to the fluctuating communication delay and quantum bit error rate (QBER). Based on our study, low performance (i.e. low power-consumption and cost-effective) CPU platforms will be sufficient for reconciliation in the existing and near-term QKD systems. Copyright © 2021, The Authors. All rights reserved.

关键词： quantum cryptography

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Deep neural network discrimination of multiplexed superconducting qubit states

arXiv

引用

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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Advancing quantum imaging through learning theory

arXiv

引用

arXiv 2025年

作者： Wang, Yunkai Oh, Changhun Liu, Junyu Jiang, Liang Zhou, Sisi Perimeter Institute for Theoretical Physics WaterlooONN2L 2Y5 Canada Department of Applied Mathematics University of Waterloo ONN2L 3G1 Canada Institute for Quantum Computing University of Waterloo ONN2L 3G1 Canada Department of Physics Korea Advanced Institute of Science and Technology Daejeon34141 Korea Republic of Department of Computer Science The University of Pittsburgh PittsburghPA15260 United States Pritzker School of Molecular Engineering The University of Chicago ChicagoIL60637 United States Department of Physics and Astronomy University of Waterloo ONN2L 3G1 Canada

We quantify performance of quantum imaging by modeling it as a learning task and calculating the Resolvable Expressive Capacity (REC). Compared to the traditionally applied Fisher information matrix approach, REC provides a single-parameter interpretation of overall imaging quality for specific measurements that applies in the regime of finite samples. We first examine imaging performance for two-point sources and generally distributed sources, referred to as compact sources, both of which have intensity distributions confined within the Rayleigh limit of the imaging system. Our findings indicate that REC increases stepwise as the sample number reaches certain thresholds, which are dependent on the source’s size. Notably, these thresholds differ between direct imaging and superresolution measurements (e.g., spatial-mode demultiplexing (SPADE) measurement in the case of Gaussian point spread functions (PSF)). REC also enables the extension of our analysis to more general scenarios involving multiple compact sources, beyond the previously studied scenarios. For closely spaced compact sources with Gaussian PSFs, our newly introduced orthogonalized SPADE method outperforms the naively separate SPADE method, as quantified by REC. Copyright © 2025, The Authors. All rights reserved.

关键词： Fisher information matrix

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RNA-2QCFA: Evolving Two-way quantum Finite Automata with Classical States for RNA Secondary Structures

arXiv

引用

arXiv 2020年

作者： Bhatia, Amandeep Singh Zheng, Shenggen Chitkara University Institute of Engineering & Technology Chitkara University Punjab India Center for Quantum Computing Peng Cheng Laboratory Shenzhen China

Recently, the use of mathematical methods and computer science applications have got significant response among biochemists and biologists to modeling the biological systems. The computational and mathematical methods have an enormous potential for modeling the deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) structures. The modeling of DNA and RNA secondary structures using automata theory had a significant impact in the fields of computer science. It is a natural goal to model the RNA secondary biomolecular structures using quantum computational models. Two-way quantum finite automata with classical states are more dominant than two-way probabilistic finite automata in language recognition. The main objective of this paper is on using two-way quantum finite automata with classical states to simulate, model and analyze the ribonucleic acid (RNA) sequences. Copyright © 2020, The Authors. All rights reserved.

关键词： RNA

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quantum continual learning of quantum data realizing knowledge backward transfer

arXiv

引用

arXiv 2022年

作者： Situ, Haozhen Lu, Tianxiang Pan, Minghua Li, Lvzhou College of Mathematics and Informatics South China Agricultural University Guangzhou510642 China Institute of Quantum Computing and Computer Theory School of Computer Science and Engineering Sun Yat-Sen University Guangzhou510006 China Guangxi Key Laboratory of Cryptography and Information Security Guilin University of Electronic Technology Guilin541004 China Department of Physics Tsinghua University Beijing100084 China

For the goal of strong artificial intelligence that can mimic human-level intelligence, AI systems would have the ability to adapt to ever-changing scenarios and learn new knowledge continuously without forgetting previously acquired knowledge. When a machine learning model is consecutively trained on multiple tasks that come in sequence, its performance on previously learned tasks may drop dramatically during the learning process of the newly seen task. To avoid this phenomenon termed catastrophic forgetting, continual learning, also known as lifelong learning, has been proposed and become one of the most up-to-date research areas of machine learning. As quantum machine learning blossoms in recent years, it is interesting to develop quantum continual learning. This paper focuses on the case of quantum models for quantum data where the computation model and the data to be processed are both quantum. The gradient episodic memory method is incorporated to design a quantum continual learning scheme that overcomes catastrophic forgetting and realizes knowledge backward transfer. Specifically, a sequence of quantum state classification tasks is continually learned by a variational quantum classifier whose parameters are optimized by a classical gradient-based optimizer. The gradient of the current task is projected to the closest gradient, avoiding the increase of the loss at previous tasks, but allowing the decrease. Numerical simulation results show that our scheme not only overcomes catastrophic forgetting, but also realize knowledge backward transfer, which means the classifier's performance on previous tasks is enhanced rather than compromised while learning a new task. Copyright © 2022, The Authors. All rights reserved.

关键词： Machine learning

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Leveraging randomized compiling for the quantum imaginary-time-evolution algorithm

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Physical Review Research 2022年第3期4卷 033140-033140页

作者： Jean-Loup Ville Alexis Morvan Akel Hashim Ravi K. Naik Marie Lu Bradley Mitchell John-Mark Kreikebaum Kevin P. O'Brien Joel J. Wallman Ian Hincks Joseph Emerson Ethan Smith Ed Younis Costin Iancu David I. Santiago Irfan Siddiqi Quantum Nanoelectronics Laboratory Dept. of Physics University of California at Berkeley Berkeley California 94720 USA Computational Research Division Lawrence Berkeley National Lab Berkeley California 94720 USA Materials Sciences Division Lawrence Berkeley National Lab Berkeley California 94720 USA Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Inst. for Quantum Computing and Dept. of Applied Mathematics University of Waterloo Waterloo Ontario Canada N2L 3G1 Quantum Benchmark Inc. Kitchener Ontario Canada N2H 5G5

Recent progress in noisy intermediate-scale quantum (NISQ) hardware shows that quantum devices may be able to tackle complex problems even without error correction. However, coherent errors due to the increased complexity of these devices is an outstanding issue. They can accumulate through a circuit, making their impact on algorithms hard to predict and mitigate. Iterative algorithms like quantum imaginary time evolution are susceptible to these errors. This article presents the combination of both noise tailoring using randomized compiling and error mitigation with purification. We also show that cycle benchmarking gives an estimate of the reliability of the purification. We apply this method to the quantum imaginary time evolution of a transverse field Ising model and report an energy estimation error and a ground-state infidelity both below 1%. Our methodology is general and can be used for other algorithms and platforms. We show how combining noise tailoring and error mitigation will push forward the performance of NISQ devices.

关键词： Measurement-based quantum computing quantum algorithms quantum benchmarking quantum computation quantum control quantum information processing quantum simulation

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Experimental study of quantum uncertainty from lack of information

arXiv

引用

arXiv 2021年

作者： Zhao, Yuan-Yuan Rozpędek, Filip Hou, Zhibo Wu, Kang-Da Xiang, Guo-Yong Li, Chuan-Feng Guo, Guang-Can Key Laboratory of Quantum Information University of Science and Technology of China CAS Hefei230026 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518055 China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei230026 China QuTech Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Kavli Institute of Nanoscience Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Pritzker School of Molecular Engineering University of Chicago ChicagoIL60637 United States

quantum uncertainty is a well-known property of quantum mechanics that states the impossibility of predicting measurement outcomes of multiple incompatible observables simultaneously. In contrast, the uncertainty in the classical domain comes from the lack of information about the exact state of the system. One may naturally ask, whether the quantum uncertainty is indeed a fully intrinsic property of the quantum theory, or whether similar to the classical domain lack of knowledge about specific parts of the physical system might be the source of this uncertainty. This question has been addressed in the previous literature where the authors argue that in the entropic formulation of the uncertainty principle that can be illustrated using the so-called, guessing games, indeed such lack of information has a significant contribution to the arising quantum uncertainty. Here we investigate this issue experimentally by implementing the corresponding two-dimensional and three-dimensional guessing games. Our results confirm that within the guessing-game framework, the quantum uncertainty to a large extent relies on the fact that quantum information determining the key properties of the game is stored in the degrees of freedom that remain inaccessible to the guessing party. Moreover, we offer an experimentally compact method to construct the high-dimensional Fourier gate which is a major building block for various tasks in quantum computation, quantum communication, and quantum metrology. Copyright © 2021, The Authors. All rights reserved.

关键词： quantum communication

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A quantum Finite Automata Approach to Modeling the Chemical Reactions

arXiv

引用

arXiv 2020年

In recent years, the modeling interest has increased significantly from the molecular level to the atomic and quantum scale. The field of computational chemistry plays a significant role in designing computational models for the operation and simulation of systems ranging from atoms and molecules to industrial-scale processes. It is influenced by a tremendous increase in computing power and the efficiency of algorithms. The representation of chemical reactions using classical automata theory in thermodynamic terms had a great influence on computer science. The study of chemical information processing with quantum computational models is a natural goal. In this paper, we have modeled chemical reactions using two-way quantum finite automata, which are halted in linear time. Additionally, classical pushdown automata can be designed for such chemical reactions with multiple stacks. It has been proven that computational versatility can be increased by combining chemical accept/reject signatures and quantum automata models. Copyright © 2020, The Authors. All rights reserved.

关键词： Chemical reactions

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