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Quafu-Qcover:Explore combinatorial optimization problems on cloud-based quantum computers

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Chinese Physics B 2024年第5期33卷 104-115页

作者：许宏泽庄伟峰王正安黄凯旋时运豪马卫国李天铭陈驰通许凯冯玉龙刘培陈墨李尚书杨智鹏钱辰靳羽欣马运恒肖骁钱鹏顾炎武柴绪丹普亚南张翼鹏魏世杰增进峰李行龙桂鲁金贻荣于海峰范桁刘东胡孟军 Beijing Academy of Quantum Information Sciences Beijing 100193China State Key Laboratory of Low Dimensional quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China Institute of Physics Chinese Academy of SciencesBeijing 100190China Frontier Science Center for quantum information Beijing 100184China School of Physical sciences University of Chinese Academy of SciencesBeijing 100190China CAS Center for Excellence in Topological quantum Computation UCASBeijing 100190China

We introduce Quafu-Qcover,an open-source cloud-based software package developed for solving combinatorial optimization problems using quantum simulators and hardware backends.Quafu-Qcover provides a standardized and comprehensive workflow that utilizes the quantum approximate optimization algorithm(QAOA).It facilitates the automatic conversion of the original problem into a quadratic unconstrained binary optimization(QUBO)model and its corresponding Ising model,which can be subsequently transformed into a weight graph.The core of Qcover relies on a graph decomposition-based classical algorithm,which efficiently derives the optimal parameters for the shallow QAOA circuit.Quafu-Qcover incorporates a dedicated compiler capable of translating QAOA circuits into physical quantum circuits that can be executed on Quafu cloud quantum computers.Compared to a general-purpose compiler,our compiler demonstrates the ability to generate shorter circuit depths,while also exhibiting superior speed performance.Additionally,the Qcover compiler has the capability to dynamically create a library of qubits coupling substructures in real-time,utilizing the most recent calibration data from the superconducting quantum devices.This ensures that computational tasks can be assigned to connected physical qubits with the highest fidelity.The Quafu-Qcover allows us to retrieve quantum computing sampling results using a task ID at any time,enabling asynchronous processing.Moreover,it incorporates modules for results preprocessing and visualization,facilitating an intuitive display of solutions for combinatorial optimization problems.We hope that Quafu-Qcover can serve as an instructive illustration for how to explore application problems on the Quafu cloud quantum computers.

关键词： quantum cloud platform combinatorial optimization problems quantum software

Ambi-chiral anomalous Hall effect in magnetically doped topological insulators

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Science China(Physics,Mechanics & Astronomy) 2022年第6期65卷 116-122页

作者： Chang Liu YunYi Zang Yan Gong Ke He XuCun Ma QiKun Xue YaYu Wang State Key Laboratory of Low Dimensional quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China Beijing Academy of Quantum Information Sciences Beijing 100193China Frontier Science Center for quantum information Beijing 100084China

The chirality associated with broken time-reversal symmetry in magnetically doped topological insulators has important implications for the quantum transport phenomena.Here we report anomalous Hall effect studies in Mn-and Cr-doped Bi_(2)Te_(3) topological insulators with varied thicknesses and doping contents.By tracing the magnitude of the anomalous Hall resistivity,we find that the Mn-type anomalous Hall effect characterized with clockwise chirality is strengthened by the reduction of film thickness,which is opposite to that of the Cr-type anomalous Hall effect with counterclockwise chirality.We provide a phenomenological physical picture to explain the evolution of the magnetic order and the anomalous Hall chirality in magnetically doped topological insulators.

关键词： topological insulator anomalous Hall effect chirality magnetic order

QCSH:A full quantum computer nuclear shell-model package

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Science China(Physics,Mechanics & Astronomy) 2023年第4期66卷 1-12页

作者： Peng Lv Shijie Wei Hao-Nan Xie Guilu Long Beijing Academy of Quantum Information Sciences Beijing 100193China State Key Laboratory of Low-Dimensional quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China

The nuclear system is a promising area for demonstrating practical quantum advantage.A comprehensive computation of a nuclear system in a classical computer is beyond the capacity of current classical computers.With the rapid development of hardware,the prospect of using quantum computers in nuclear physics is close at hand.In this paper,we report a full quantum package,QCSH,for solving a nuclear shell model in a quantum computer.QCSH uses the linear combination of the unitary formalism of quantum computing and performs all calculations in a quantum computer.The complexities of qubit resource and the number of basic gates of QCSH are both polynomials to the number of nucleons in nuclei.For example,QCSH is used to calculate the binding energies of 12 light nuclei(i.e.,^(2)H,^(3)H,^(3)He,^(4)He,^(6)Li,^(7)Li,^(12)C,^(14)N,^(16)O,^(17)O,^(23)Na,and^(40)Ca).Moreover,we experimentally demonstrate the calculation of deuteron binding energy using a superconducting quantum processor.The result indicates that QCSH can provide meaningful results already in near-term quantum devices.

关键词： quanutm simulation nuclear shell model linear combination of unitary operations quantum gradient descent

Observation of 1D Fermi arc states in Weyl semimetal TaAs

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National Science Review 2022年第8期9卷 62-70页

作者： Xiaohu Zheng Qiangqiang Gu Yiyuan Liu Bingbing Tong Jian-Feng Zhang Chi Zhang Shuang Jia Ji Feng Rui-Rui Du International Center for quantum Materials School of PhysicsPeking University Collaborative Innovation Center of quantum Matter State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of Sciences CAS Center for Excellence in Topological quantum Computation University of Chinese Academy of Sciences Beijing Academy of Quantum Information Sciences

Fermi arcs on Weyl semimetals exhibit many exotic quantum phenomena. Usually found on atomically flat surfaces with approximate translation symmetry, Fermi arcs are rooted in the peculiar topology of bulk Bloch bands of 3D crystals. The fundamental question of whether a 1D Fermi arc can be probed remains unanswered. Such an answer could significantly broaden potential applications of Weyl semimetals. Here,we report a direct observation of robust edge states on atomic-scale ledges in TaAs using low-temperature scanning tunneling microscopy/spectroscopy. Spectroscopic signatures and theoretical calculations reveal that the 1D Fermi arcs arise from the chiral Weyl points of bulk crystals. The crossover from 2D Fermi arcs to eventual complete localization on 1D edges was arrested experimentally on a sequence of surfaces. Our results demonstrate extreme robustness of the bulk-boundary correspondence, which offers topological protection for Fermi arcs, even in cases in which the boundaries are at the atomic-scale. The persistent 1D Fermi arcs can be profitably exploited in miniaturized quantum devices.

关键词： Weyl semimetals Fermi arc edge states chiral Weyl points TaAs scanning tunneling microscopy/spectroscopy

Quafu-RL:The cloud quantum computers based quantum reinforcement learning

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Chinese Physics B 2024年第5期33卷 29-34页

作者：靳羽欣许宏泽王正安庄伟峰黄凯旋时运豪马卫国李天铭陈驰通许凯冯玉龙刘培陈墨李尚书杨智鹏钱辰马运恒肖骁钱鹏顾炎武柴绪丹普亚南张翼鹏魏世杰曾进峰李行龙桂鲁金贻荣于海峰范桁刘东胡孟军 Beijing Academy of Quantum Information Sciences Beijing 100193China State Key Laboratory of Low Dimensional quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China Institute of Physics Chinese Academy of SciencesBeijing 100190China Frontier Science Center for quantum information Beijing 100184China School of Physical sciences University of Chinese Academy of SciencesBeijing 100190China CAS Center for Excellence in Topological quantum Computation University of Chinese Academy of SciencesBeijing 100190China School of Mathematical sciences Nankai UniversityTianjin 300071China

With the rapid advancement of quantum computing,hybrid quantum–classical machine learning has shown numerous potential applications at the current stage,with expectations of being achievable in the noisy intermediate-scale quantum(NISQ)era.quantum reinforcement learning,as an indispensable study,has recently demonstrated its ability to solve standard benchmark environments with formally provable theoretical advantages over classical counterparts.However,despite the progress of quantum processors and the emergence of quantum computing clouds,implementing quantum reinforcement learning algorithms utilizing parameterized quantum circuits(PQCs)on NISQ devices remains infrequent.In this work,we take the first step towards executing benchmark quantum reinforcement problems on real devices equipped with at most 136 qubits on the BAQIS Quafu quantum computing cloud.The experimental results demonstrate that the policy agents can successfully accomplish objectives under modified conditions in both the training and inference phases.Moreover,we design hardware-efficient PQC architectures in the quantum model using a multi-objective evolutionary algorithm and develop a learning algorithm that is adaptable to quantum devices.We hope that the Quafu-RL can be a guiding example to show how to realize machine learning tasks by taking advantage of quantum computers on the quantum cloud platform.

关键词： quantum cloud platform quantum reinforcement learning evolutionary quantum architecture search

Characterizing noise correlation and enhancing coherence via qubit motion

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Fundamental Research 2021年第1期1卷 10-15页

作者： Jiaxiu Han Zhiyuan Li Jingning Zhang Huikai Xu Kehuan Linghu Yongchao Li Chengyao Li Mo Chen Zhen Yang Junhua Wang Teng Ma Guangming Xue Yirong Jin Haifeng Yu Beijing Academy of Quantum Information Sciences Beijing 100193China

The identification of spacial noise correlation is of critical importance in developing error-corrected quantum devices,but it has barely been studied so far.In this work,we utilize an effective method called qubit motion,to efficiently determine the noise correlations between any pair of qubits in a 7-qubit superconducting quantum system.The noise correlations between the same pairs of qubits are also investigated when the qubits are at distinct operating frequencies.What’s more,in this multi-qubit system with the presence of noise correlations,we demonstrate the enhancing effect of qubit motion on the coherence of logic qubits,and we propose a Motion-CPMG operation sequence to more efficiently protect the logic state from decoherence,which is experimentally demonstrated to extend the coherence time of logic qubits by nearly one order of magnitude.

关键词： Qubit motion Noise correlation Decoherence CPMG quantum error correction

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基于简并p轨道的平带模型及其二维材料实现

Science Bulletin 2021年第8期66卷 765-770,M0003页

作者：曾犟鹿鸣刘海文江华谢心澄 International Center for quantum Materials School of PhysicsPeking UniversityBeijing 100871China Beijing Academy of Quantum Information Sciences Beijing 100871China Center for Advanced quantum Studies Department of PhysicsBeijing Normal UniversityBeijing 100875China School of Physical Science and Technology Soochow UniversitySuzhou 215006China Beijing Academy of Quantum Information Sciences Beijing 100193China CAS Center for Excellence in Topological quantum Computation University of Chinese Academy of SciencesBeijing 100871China

作为一种无色散且态密度发散的电子结构,平带为研究相互作用、实现新奇物理性质提供了理想平台.设计理论模型并寻找相应的材料实现受到了广泛关注.当前,基于现有理论模型寻找和制备具有理想平带的二维材料仍存在不同程度的挑战.本文提... 详细信息

作为一种无色散且态密度发散的电子结构,平带为研究相互作用、实现新奇物理性质提供了理想平台.设计理论模型并寻找相应的材料实现受到了广泛关注.当前,基于现有理论模型寻找和制备具有理想平带的二维材料仍存在不同程度的挑战.本文提出了一种可以在一系列二维材料中实现平带的新型理论模型.以结构稳定的硫化钾(K2S)二维单层为例,其平带的色散仅为50毫电子伏左右.在硫化钾单层与石墨烯构成的异质结中,层间的电荷转移可以调节平带的部分填充.该平带模型还可以在一些1T结构的三元化合物中实现.例如,已经被实验室合成的Gd2CCl2.第一性原理计算表明,在铁磁态的Gd2CCl2单层中,还可以实现自旋极化的平带.此文提出的理论模型与二维材料为平带以及相关新奇物理性质的研究提供了理想的且可实现的平台.

关键词：三元化合物二维材料电荷转移自旋极化部分填充第一性原理计算理论模型平带

Near-term quantum computing techniques: Variational quantum algorithms, error mitigation, circuit compilation, benchmarking and classical simulation

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Science China(Physics,Mechanics & Astronomy) 2023年第5期66卷 23-72页

作者： He-Liang Huang Xiao-Yue Xu Chu Guo Guojing Tian Shi-Jie Wei Xiaoming Sun Wan-Su Bao Gui-Lu Long Henan Key Laboratory of quantum information and Cryptography Zhengzhou 450000China State Key Lab of Processors Institute of Computing TechnologyChinese Academy of SciencesBeijing 100190China School of Computer Science and Technology University of Chinese Academy of SciencesBeijing 100049China Beijing Academy of Quantum Information Sciences Beijing 100193China Department of Physics Tsinghua UniversityBeijing 100084China

quantum computing is a game-changing technology for global academia,research centers and industries including computational science,mathematics,finance,pharmaceutical,materials science,chemistry and cryptography.Although it has seen a major boost in the last decade,we are still a long way from reaching the maturity of a full-fledged quantum computer.That said,we will be in the noisy-intermediate scale quantum(NISQ)era for a long time,working on dozens or even thousands of qubits quantum computing systems.An outstanding challenge,then,is to come up with an application that can reliably carry out a nontrivial task of interest on the near-term quantum devices with non-negligible quantum noise.To address this challenge,several near-term quantum computing techniques,including variational quantum algorithms,error mitigation,quantum circuit compilation and benchmarking protocols,have been proposed to characterize and mitigate errors,and to implement algorithms with a certain resistance to noise,so as to enhance the capabilities of near-term quantum devices and explore the boundaries of their ability to realize useful applications.Besides,the development of near-term quantum devices is inseparable from the efficient classical sim-ulation,which plays a vital role in quantum algorithm design and verification,error-tolerant verification and other applications.This review will provide a thorough introduction of these near-term quantum computing techniques,report on their progress,and finally discuss the future prospect of these techniques,which we hope will motivate researchers to undertake additional studies in this field.

关键词： quantum computing noisy-intermediate scale quantum variational quantum algorithms error mitigation circuit com-pilation benchmarking protocols classical simulation

All-electrical switching of a topological non-collinear antiferromagnet at room temperature

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National Science Review 2023年第2期10卷 123-130页

作者： Yongcheng Deng Xionghua Liu Yiyuan Chen Zongzheng Du Nai Jiang Chao Shen Enze Zhang Houzhi Zheng Hai-Zhou Lu Kaiyou Wang State Key Laboratory for Superlattices and Microstructures Institute of SemiconductorsChinese Academy of Sciences Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Institute for quantum Science and Engineering and Department of Physics Southern University of Science and Technology (SUSTech) International quantum academy Beijing Academy of Quantum Information Sciences Center for Excellence in Topological quantum Computation University of Chinese Academy of Sciences

Non-collinear antiferromagnetic Weyl semimetals,combining the advantages of a zero stray field and ultrafast spin dynamics,as well as a large anomalous Hall effect and the chiral anomaly of Weyl fermions,have attracted extensive interest.However,the all-electrical control of such systems at room temperature,a crucial step toward practical application,has not been reported.Here,using a small writing current density of around 5 × 106A·cm-2,we realize the all-electrical current-induced deterministic switching of the non-collinear antiferromagnet Mn3Sn,with a strong readout signal at room temperature in the Si/SiO2/Mn3Sn/AlOxstructure,and without external magnetic field or injected spin current.Our simulations reveal that the switching originates from the current-induced intrinsic non-collinear spin-orbit torques in Mn3Sn itself.Our findings pave the way for the development of topological antiferromagnetic spintronics.

关键词： spintronics non-collinear antiferromagnetic Weyl semimetals all-electrical switching spin-orbit torques