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arXiv 2023年

作者： Zhang, Xinfang Wu, Zhihao White, Gregory A.L. Xiang, Zhongcheng Hu, Shun Peng, Zhihui Liu, Yong Zheng, Dongning Fu, Xiang Huang, Anqi Poletti, Dario Modi, Kavan Wu, Junjie Deng, Mingtang Guo, Chu 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 and Astronomy Monash University VIC3800 Australia Dahlem Center for Complex Quantum Systems Freie Universität Berlin Berlin14195 Germany Institute of Physics Chinese Academy of Sciences Beijing100190 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Science Mathematics and Technology Cluster and Engineering Product Development Pillar Singapore University of Technology and Design 8 Somapah Road 487372 Singapore Centre for Quantum Technologies National University of Singapore 117543 Singapore MajuLab CNRS-UNS-NUS-NTU International Joint Research Unit UMI 3654 Singapore Quantum for NSW Sydney2000 Australia

The development of fault-tolerant quantum processors relies on the ability to control noise. A particularly insidious form of noise is temporally correlated or non-Markovian noise. By combining randomized benchmarking with supervised machine learning algorithms, we develop a method to learn the details of temporally correlated noise. In particular, we can learn the time-independent evolution operator of system plus bath and this leads to (i) the ability to characterize the degree of non-Markovianity of the dynamics and (ii) the ability to predict the dynamics of the system even beyond the times we have used to train our model. We exemplify this by implementing our method on a superconducting quantum processor. Our experimental results show a drastic change between the Markovian and non-Markovian regimes for the learning accuracies. Copyright © 2023, The Authors. All rights reserved.

关键词： Benchmarking

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Nonreciprocal coherent coupling of nanomagnets by exchange spin waves

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Nano Research 2021年第7期14卷 2133-2138页

作者： Hanchen Wang Jilei Chen Tao Yu Chuanpu Liu Chenyang Guo Song Liu Ka Shen Hao Jia Tao Liu Jianyu Zhang Marco A.Cabero Z Qiuming Song Sa Tu Mingzhong Wu Xiufeng Han Ke Xia Dapeng Yu Gerrit E.W.Bauer Haiming Yu Fert Beijing Institute School of Integrated Circuit Science and EngineeringBeijing Advanced Innovation Center for Big Data and Brain ComputingBeihang UniversityBeijing 100191China Max Planck Institute for the Structure and Dynamics of Matter 22761 HamburgGermany Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsUniversity of Chinese Academy of SciencesChinese Academy of SciencesBeijing 100190China Shenzhen Institute for Quantum Science and Engineering(SIQSE) and Department of PhysicsSouthern University of Science and Technology(SUSTech)Shenzhen 518055China Department of Physics Beijing Normal UniversityBeijing 100875China Department of Physics Colorado State UniversityFort CollinsColorado 80523USA Kavli Institute of Nanoscience Delft University of Technology2628 CJ DelftThe Netherlands Institute for Materials Research WPI-AIMR and CSNRTohoku UniversitySendai 980-8577Japan Zernike Institute for Advanced Materials University of GroningenGroningenNijenborgh 49747 AG GroningenThe Netherlands

Nanomagnets are widely used to store information in non-volatile spintronic *** waves can transfer information with low-power consumption as their propagations are independent of charge ***,to dynamically couple two distant nanomagnets via spin waves remains a major challenge for *** we experimentally demonstrate coherent coupling of two distant Co nanowires by fast propagating spin waves in an yttrium iron garnet thin film with sub-50 nm *** in two nanomagnets are unidirectionally phase-locked with phase shifts controlled by magnon spin torque and spin-wave *** coupled system is finally formulated by an analytical theory in terms of an effective non-Hermitian *** results are attractive for analog neuromorphic computing that requires unidirectional information transmission.

关键词： spintronics nanomagnets spin waves coherent coupling nonreciprocity

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Distributed Deutsch-Jozsa Algorithm

SSRN

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SSRN 2024年

作者： Li, Hao Qiu, Daowen Luo, Le Institute of Quantum Computing and Software School of Computer Science and Engineering Sun Yat-sen University Guangzhou510006 China School of Physics and Astronomy Sun Yat-sen University Zhuhai519082 China The Guangdong Key Laboratory of Information Security Technology Sun Yat-sen University Guangzhou510006 China QUDOOR Technologies Inc. Zhuhai China

Deutsch-Jozsa (DJ) problem is one of the most important problems demonstrating the power of quantum algorithm, which can be described as a Boolean function $f: \{0,1\}^n\rightarrow \{0,1\}$ with promising it is either constant or balanced, and the purpose is to determine which type it is. DJ algorithm can compute it exactly with one query. However, classical deterministic algorithm requires $2^{n-1} + 1$ queries to compute it in the worse case. Therefore, DJ algorithm is essentially faster than any possible classical deterministic algorithm for computing DJ problem. In this paper, we discover the intrinsic structure of DJ problem in distributed scenario by giving a number of equivalence characterizations between $f$ being constant (balanced) and some properties of $f$'s subfunctions. We propose three distributed DJ algorithms, which have essential acceleration compared to distributed classical deterministic DJ algorithm. In comparison to DJ algorithm, our algorithms can reduce the number of qubits for a single computing node. Furthermore, compared to distributed DJ algorithm with errors, our algorithms possess accuracy and improved scalability. © 2024, The Authors. All rights reserved.

关键词： Boolean functions

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Generation of cat states by a weak parametric drive and a transitionless tracking algorithm

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Physical Review A 2022年第4期106卷 042430-042430页

作者： Shuai Liu Ye-Hong Chen Yu Wang Yi-Hao Kang Zhi-Cheng Shi Jie Song Yan Xia Fujian Key Laboratory of Quantum Information and Quantum Optics (Fuzhou University) Fuzhou 350116 China Department of Physics Fuzhou University Fuzhou 350116 China School of Physics and Electronic Engineering Hubei University of Arts and Science Xiangyang 441053 China Theoretical Quantum Physics Laboratory RIKEN Cluster for Pioneering Research Wako-shi Saitama 351-0198 Japan RIKEN Center for Quantum Computing (RQC) 2-1 Hirosawa Wako-shi Saitama 351-0198 Japan Department of Physics Harbin Institute of Technology Harbin 150001 China

In this paper, we present an experimentally feasible protocol to generate the cat states in the microwave resonator coupled to a superconducting qubit. The setup employs a detuned, time-dependent parametric drive to squeeze the resonator mode so that an adjustable qubit-resonator coupling strength can be obtained. Therefore, based on the transitionless tracking algorithm, we can design control pulses to generate the qubit-resonator entangled states with high fidelity in the laboratory frame. Then, the even and odd cat states can be further obtained by performing measurement on the superconducting qubit. Compared to the scheme [Chen et al., Phys. Rev. Lett. 126, 023602 (2021)], the present protocol is realized in the regime of weak parametric drive. In the case, squeezing-induced noise can be reduced so that the fidelity of the generated state can be improved. Numerical simulations indicate that the present protocol is well executed under experimentally available parameters. Thus, the protocol is feasible with the present state of the art in microwave superconducting circuits.

关键词： quantum control quantum information processing quantum optics

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Landau–Zener–Stückelberg Interference in Nonlinear Regime

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Chinese Physics Letters 2019年第12期36卷 36-39页

作者： Tong Wu Yuxuan Zhou Yuan Xu Song Liu Jian Li Department of Physics Harbin Institute of TechnologyHarbin 150001 Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and TechnologyShenzhen 518055 Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and TechnologyShenzhen 518055 Center for Quantum Computing Peng Cheng LaboratoryShenzhen 518055

Landau-Zener-Stückelberg(LZS)interference has drawn renewed attention to quantum information processing research because it is not only an effective tool for characterizing two-level quantum systems but also a powerful approach to manipulate quantum *** quantum circuits,due to their versatile tunability and degrees of control,are ideal platforms for studying LZS interference *** use a superconducting Xmon qubit to study LZS interference by parametrically modulating the qubit transition frequency *** dc flux biasing of the qubit slightly far away from the optimal flux point,the qubit excited state population shows an interference pattern that is very similar to the standard LZS interference in linear regime,except that all bands shift towards lower frequencies when increasing the rf modulation *** dc flux biasing close to the optimal flux point,the negative sidebands and the positive sidebands behave differently,resulting in an asymmetric interference *** experimental results are also in good agreement with our analytical and numerical simulations.

关键词： bands quantum Landau

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Clifford-deformed Surface Codes

arXiv

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arXiv 2022年

作者： Dua, Arpit Kubica, Aleksander Jiang, Liang Flammia, Steven T. Gullans, Michael J. Department of Physics Institute for Quantum Information and Matter California Institute of Technology PasadenaCA91125 United States AWS Center for Quantum Computing PasadenaCA91125 United States California Institute of Technology PasadenaCA91125 United States Pritzker School of Molecular Engineering The University of Chicago IL60637 United States Joint Center for Quantum Information and Computer Science NIST University of Maryland College ParkMD20742 United States

Various realizations of Kitaev’s surface code perform surprisingly well for biased Pauli noise. Attracted by these potential gains, we study the performance of Clifford-deformed surface codes (CDSCs) obtained from the surface code by applying single-qubit Clifford operators. We first analyze CDSCs on the 3 × 3 square lattice and find that, depending on the noise bias, their logical error rates can differ by orders of magnitude. To explain the observed behavior, we introduce the effective distance d′, which reduces to the standard distance for unbiased noise. To study CDSC performance in the thermodynamic limit, we focus on random CDSCs. Using the statistical mechanical mapping for quantum codes, we uncover a phase diagram that describes random CDSC families with 50% threshold at infinite bias. In the high-threshold region, we further demonstrate that typical code realizations outperform the thresholds and subthreshold logical error rates, at finite bias, of the best-known translationally invariant codes. We demonstrate the practical relevance of these random CDSC families by constructing a translation-invariant CDSC belonging to a high-performance random CDSC family. We also show that our translation-invariant CDSC outperforms well-known translation-invariant CDSCs such as the XZZX and XY codes. Copyright © 2022, The Authors. All rights reserved.

关键词： Qubits

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Noisy intermediate-scale quantum computers

arXiv

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arXiv 2023年

作者： Cheng, Bin Deng, Xiu-Hao Gu, Xiu He, Yu Hu, Guangchong Huang, Peihao Li, Jun Lin, Ben-Chuan Lu, Dawei Lu, Yao Qiu, Chudan Wang, Hui Xin, Tao Yu, Shi Yung, Man-Hong Zeng, Junkai Zhang, Song Zhong, Youpeng Peng, Xinhua Nori, Franco Yu, Dapeng Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China International Quantum Academy Shenzhen518048 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Department of Physics Southern University of Science and Technology Shenzhen518055 China Hefei National Research Center for Physical Sciences the Microscale School of Physical Sciences 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 Hefei National Laboratory University of Science and Technology of China Hefei230088 China CAS Key Laboratory of Microscale Magnetic Resonance School of Physical Sciences University of Science and Technology of China Hefei230026 China Quantum Computing Center Cluster for Pioneering Research RIKEN Wakoshi Saitama351-0198 Japan Physics Department University of Michigan Ann ArborMI48109-1040 United States

quantum computers have made extraordinary progress over the past decade, and significant milestones have been achieved along the path of pursuing universal fault-tolerant quantum computers. quantum advantage, the tipping point heralding the quantum era, has been accomplished along with several waves of breakthroughs. quantum hardware has become more integrated and architectural compared to its toddler days. The controlling precision of various physical systems is pushed beyond the fault-tolerant threshold. Meanwhile, quantum computation research has established a new norm by embracing industrialization and commercialization. The joint power of governments, private investors, and tech companies has significantly shaped a new vibrant environment that accelerates the development of this field, now at the beginning of the noisy intermediate-scale quantum era. Here, we first discuss the progress achieved in the field of quantum computation by reviewing the most important algorithms and advances in the most promising technical routes, and then summarizing the next-stage challenges. Furthermore, we illustrate our confidence that solid foundations have been built for the fault-tolerant quantum computer and our optimism that the emergence of quantum killer applications essential for human society shall happen in the future. © 2023, CC BY.

关键词： Fault tolerance

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Assessing the source of error in the Thomas-Fermi-von Weizsäcker density functional

arXiv

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arXiv 2023年

作者： Thapa, Bishal Jing, Xin Pask, John E. Suryanarayana, Phanish Mazin, Igor I. Department of Physics and Astronomy George Mason University FairfaxVA22030 United States Quantum Science and Engineering Center George Mason University FairfaxVA22030 United States College of Engineering Georgia Institute of Technology AtlantaGA30332 United States College of Computing Georgia Institute of Technology AtlantaGA30332 United States Physics Division Lawrence Livermore National Laboratory LivermoreCA94550 United States

We investigate the source of error in the Thomas-Fermi-von Weizsäcker (TFW) density functional relative to Kohn-Sham density functional theory (DFT). In particular, through numerical studies on a range of materials, for a variety of crystal structures subject to strain and atomic displacements, we find that while the ground state electron density in TFW orbital-free DFT is close to the Kohn-Sham density, the corresponding energy deviates significantly from the Kohn-Sham value. We show that these differences are a consequence of the poor representation of the linear response within the TFW approximation for the electronic kinetic energy, confirming conjectures in the literature. In so doing, we find that the energy computed from a non-self-consistent Kohn-Sham calculation using the TFW electronic ground state density is in very good agreement with that obtained from the fully self-consistent Kohn-Sham solution. Copyright © 2023, The Authors. All rights reserved.

关键词： Kinetics

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Tailored XZZX codes for biased noise

arXiv

引用

arXiv 2022年

作者： Xu, Qian Mannucci, Nam Seif, Alireza Kubica, Aleksander Flammia, Steven T. Jiang, Liang Pritzker School of Molecular Engineering The University of Chicago ChicagoIL60637 United States AWS Center for Quantum Computing PasadenaCA91125 United States California Institute of Technology PasadenaCA91125 United States

quantum error correction (QEC) for generic errors is challenging due to the demanding threshold and resource requirements. Interestingly, when physical noise is biased, we can tailor our QEC schemes to the noise to improve performance. Here we study a family of codes having XZZX-type stabilizer generators, including a set of cyclic codes generalized from the five-qubit code and a set of topological codes that we call generalized toric codes (GTCs). We show that these XZZX codes are highly qubit efficient if tailored to biased noise. To characterize the code performance, we use the notion of effective distance, which generalizes code distance to the case of biased noise and constitutes a proxy for the logical failure rate. We find that the XZZX codes can achieve a favorable resource scaling by this metric under biased noise. We also show that the XZZX codes have remarkably high thresholds that reach what is achievable by random codes, and furthermore they can be efficiently decoded using matching decoders. Finally, by adding only one flag qubit, the XZZX codes can realize fault-tolerant QEC while preserving their large effective distance. In combination, our results show that tailored XZZX codes give a resource-efficient scheme for fault-tolerant QEC against biased noise. © 2022, CC BY-NC-ND.

关键词： Error correction

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Preparing quantum States by Measurement-feedback Control with Bayesian Optimization

arXiv

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arXiv 2022年

作者： Wu, Yadong Yao, Juan Zhang, Pengfei Department of Physics Fudan University Shanghai200438 China Fudan University Shanghai200438 China Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai200433 China Shanghai Qi Zhi Institute AI Tower Xuhui District Shanghai200232 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Guangdong Shenzhen518055 China International Quantum Academy Guangdong Shenzhen518048 China Guangdong Provincial Key Laboratory ofQuantum Science and Engineering Southern University of Science and Technology Guangdong Shenzhen518055 China Walter Burke Institute for Theoretical Physics Institute for Quantum Information and Matter California Institute of Technology PasadenaCA91125 United States

Preparation of quantum states is of vital importance for performing quantum computations and quantum simulations. In this work, we propose a general framework for preparing ground states of many-body systems by combining the measurement-feedback control process (MFCP) and the machine learning method. Using the Bayesian optimization (BO) strategy, the efficiency of determining the measurement and feedback operators in the MFCP is demonstrated. Taking the one dimensional Bose-Hubbard model as an example, we show that BO can generate optimal parameters, although constrained by the operator basis, which can drive the system to the low energy state with high probability in typical quantum trajectories. Copyright © 2022, The Authors. All rights reserved.

关键词： Feedback control

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