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Photoionisation detection of a single Er3+ ion with sub-100-ns time resolution

National Science Review 2024年第4期11卷 38-45页

作者： Yangbo Zhang Wenda Fan Jiliang Yang Hao Guan Qi Zhang Xi Qin Changkui Duan Gabriele G.de Boo Brett C.Johnson Jeffrey C.Mc Callum Matthew J.Sellars Sven Rogge Chunming Yin Jiangfeng Du CAS Key laboratory of Microscale Magnetic Resonance and School of Physical Sciences University of Science and Technology of China CAS Center for Excellence in quantum Information and quantum Physics University of Science and Technology of China Hefei National laboratory University of Science and Technology of China Centre of Excellence for quantum computation and communication Technology School of Physics University of New South Wales Centre of Excellence for quantum computation and communication Technology School of Engineering RMIT University Centre of Excellence for quantum computation and communication Technology School of Physics University of Melbourne Centre of Excellence for quantum computation and communication Technology Research School of Physics and Engineering Australian National University

Efficient detection of single optical centres in solids is essential for quantum information processing, sensing and single-photon generation *** this work,we use radio-frequency（RF） reflectometry to electrically detect the photoionisation induced by a single Er3+ion in *** high bandwidth and sensitivity of the RF reflectometry provide sub-100-ns time resolution for the photoionisation *** this technique,the optically excited state lifetime of a single Er3+ion in a Si nano-transistor is measured for the first time to be 0.49±0.04μ*** results demonstrate an efficient approach for detecting a charge state change induced by Er excitation and *** approach could be used for fast readout of other single optical centres in solids and is attractive for large-scale integrated optical quantum systems thanks to the multi-channel RF reflectometry demonstrated with frequency multiplexing techniques.

关键词： single optical centres erbium ions RF reflectometry photoionisation detection

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Layer Hall effect induced by hidden Berry curvature in antiferromagnetic insulators

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National Science Review 2024年第2期11卷 15-23页

作者： Rui Chen Hai-Peng Sun Mingqiang Gu Chun-Bo Hua Qihang Liu Hai-Zhou Lu X.C.Xie Shenzhen Institute for quantum Science and Engineering and Department of Physics Southern University of Science and Technology(SUSTech) International quantum Academy Institute for Theoretical Physics and Astrophysics University of Würzburg School of Electronic and Information Engineering Hubei University of Science and Technology Guangdong Provincial Key laboratory of computational Science and Material Design Southern University of Science and Technology Shenzhen Key laboratory of quantum Science and Engineering International Center for quantum Materials School of PhysicsPeking University Collaborative Innovation Center of quantum Matter CAS Center for Excellence in Topological quantum computation University of Chinese Academy of Sciences

The layer Hall effect describes electrons spontaneously deflected to opposite sides at different layers, which has been experimentally reported in the MnBi2Te4thin films under perpendicular electric fields. Here, we reveal a universal origin of the layer Hall effect in terms of the so-called hidden Berry curvature, as well as material design principles. Hence, it gives rise to zero Berry curvature in momentum space but non-zero layer-locked hidden Berry curvature in real space. We show that, compared to that of a trivial insulator, the layer Hall effect is significantly enhanced in antiferromagnetic topological insulators. Our universal picture provides a paradigm for revealing the hidden physics as a result of the interplay between the global and local symmetries, and can be generalized in various scenarios.

关键词： layerHall effect hidden Berry curvature antiferromagnetic insulator axion insulator, quantum transport

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quantum self-attention neural networks for text classification

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Science China(Information Sciences) 2024年第4期67卷 301-313页

作者： Guangxi LI Xuanqiang ZHAO Xin WANG Institute for quantum Computing Baidu Research Centre for quantum Software and Information University of Technology Sydney QICI quantum Information and computation Initiative Department of Computer ScienceThe University of Hong Kong Thrust of Artificial Intelligence Information HubHong Kong University of Science and Technology(Guangzhou)

An emerging direction of quantum computing is to establish meaningful quantum applications in various fields of artificial intelligence, including natural language processing(NLP). Although some efforts based on syntactic analysis have opened the door to research in quantum NLP(QNLP), limitations such as heavy syntactic preprocessing and syntax-dependent network architecture make them impracticable on larger and real-world data sets. In this paper, we propose a new simple network architecture, called the quantum selfattention neural network(QSANN), which can compensate for these limitations. Specifically, we introduce the self-attention mechanism into quantum neural networks and then utilize a Gaussian projected quantum self-attention serving as a sensible quantum version of self-attention. As a result, QSANN is effective and scalable on larger data sets and has the desirable property of being implementable on near-term quantum devices. In particular, our QSANN outperforms the best existing QNLP model based on syntactic analysis as well as a simple classical self-attention neural network in numerical experiments of text classification tasks on public data sets. We further show that our method exhibits robustness to low-level quantum noises and showcases resilience to quantum neural network architectures.

关键词： quantum neural networks self-attention natural language processing text classification parameterized quantum circuits

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High-Resolution Recognition of Orbital Angular Momentum Modes in Asymmetric Bessel Beams Assisted by Deep Learning

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Chinese Physics Letters 2024年第7期41卷 27-35页

作者：徐鹏飞童鑫曾子帅刘书悉赵道木 Zhejiang Key laboratory of Micro-nano quantum Chips and quantum Control School of PhysicsZhejiang UniversityHangzhou 310058China

Fractional orbital angular momentum(OAM) vortex beams present a promising way to increase the data throughput in optical communication systems. Nevertheless, high-precision recognition of fractional OAM with different propagation distances remains a significant challenge. We develop a convolutional neural network(CNN)method to realize high-resolution recognition of OAM modalities, leveraging asymmetric Bessel beams imbued with fractional OAM. Experimental results prove that our method achieves a recognition accuracy exceeding 94.3% for OAM modes, with an interval of 0.05, and maintains a high recognition accuracy above 92% across varying propagation distances. The findings of our research will be poised to significantly contribute to the deployment of fractional OAM beams within the domain of optical communications.

关键词： Bessel fractional Orbital

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Determination of molecular energies via variational-based quantum imaginary time evolution in a superconducting qubit system

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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 1-11页

作者： Zhiwen Zong Sainan Huai Tianqi Cai Wenyan Jin Ze Zhan Zhenxing Zhang Kunliang Bu Liyang Sui Ying Fei Yicong Zheng Shengyu Zhang Jianlan Wu Yi Yin Zhejiang Province Key laboratory of quantum Technology and Device School of PhysicsZhejiang UniversityHangzhou 310027China Tencent quantum laboratory Shenzhen 518057China

As a valid tool for solving ground state problems,imaginary time evolution(ITE)is widely used in physical and chemical *** ITE-based algorithms in their quantum counterpart have recently been proposed and applied to some real *** experimentally realize the variational-based quantum imaginary time evolution(QITE)algorithm to simulate the ground state energy of hydrogen(H_2)and lithium hydride(Li H)molecules in a superconducting qubit *** H_2 molecule is directly simulated using the 3-qubit circuit with unitary-coupled clusters(UCC)*** also combine QITE with the cluster mean-field(CMF)method to obtain an effective *** Li H molecule is correspondingly simulated using the 3-qubit circuit with hardware-efficient *** comparison,the Li H molecule is also directly simulated using the 4-qubit circuit with UCC ansatz at the equilibrium *** the experimental results show a convergence within 4 iterations,with high-fidelity ground state energy *** a more complex system in the future,the CMF may allow further grouping of interactions to obtain an effective Hamiltonian,then the hybrid QITE algorithm can possibly simulate a relatively large-scale system with fewer qubits.

关键词： quantum computation quantum algorithm superconducting qubit

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quantum nonlocality evolution for two entangled mesoscopic fields under decoherence

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communications in Theoretical Physics 2024年第1期76卷 24-28页

作者： Zhao-Song Tan Shou-Bang Yang Zhen-Biao Yang Shi-Biao Zheng Fujian Key laboratory of quantum Information and quantum Optics Fuzhou UniversityFuzhouFujian 350116China

Investigation of the nonlocality evolution of entangled mesoscopic fields under decoherence not only is important for understanding the quantum–classical transition,but also has relevance to quantum communication and quantum computation protocols based on continuous *** to previous formulations of Bell inequalities,the system loses nonlocal features far before the disappearance of *** here construct a new version of Bell signal based on rotated and displaced on–off correlations,with which the Bell inequality is violated as long as there remains entanglement and the field state components keep ***,the nonlocal character revealed by our formulation decays much slower compared with those based on previous *** importantly,there exists a wide regime where the Bell inequality is restored with previous formulations but remains to be violated based on our correlation operators.

关键词： entangled mesoscopic fields rotated and displaced on-off correlations Bell inequality nonlocality evolution

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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 ***-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 *** core of Qcover relies on a graph decomposition-based classical algorithm,which efficiently derives the optimal parameters for the shallow QAOA ***-Qcover incorporates a dedicated compiler capable of translating QAOA circuits into physical quantum circuits that can be executed on Quafu cloud quantum *** to a general-purpose compiler,our compiler demonstrates the ability to generate shorter circuit depths,while also exhibiting superior speed ***,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 *** ensures that computational tasks can be assigned to connected physical qubits with the highest *** Quafu-Qcover allows us to retrieve quantum computing sampling results using a task ID at any time,enabling asynchronous ***,it incorporates modules for results preprocessing and visualization,facilitating an intuitive display of solutions for combinatorial optimization *** 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

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Continuous variable quantum teleportation and remote state preparation between two space-separated local networks

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Science China(Information Sciences) 2024年第4期67卷 314-322页

作者： Siyu REN Dongmei HAN Meihong WANG Xiaolong SU State Key laboratory of quantum Optics and quantum Optics Devices Institute of Opto-ElectronicsShanxi University Collaborative Innovation Center of Extreme Optics Shanxi University

Implementing quantum communication between space-separated local networks is essential for designing global quantum networks. In this study, we propose quantum teleportation and remote state preparation schemes between users of two space-separated local networks established by continuous-variable multipartite entangled states. In the proposed schemes, the quantum nodes belonging to the two distant local networks are first entangled by entanglement swapping, and then quantum communication protocols are realized. We show that quantum teleportation between any two users belonging to space-separated local networks can be realized with the assistance of other users, and squeezed thermal states can be remotely prepared in one local network by performing a homodyne projective measurement on the state in another distant local network. Our results provide a feasible approach for quantum communication between spaceseparated quantum networks with multipartite entangled states.

关键词： quantum communication quantum network quantum teleportation remote state preparation entanglement swapping continuous variable

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Security of quantum key distribution with virtual mutually unbiased bases

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 13-21页

作者： Hong-Wei Li Chen-Peng Hao Zhi-Jiang Chen Li Gong Yi-Fei Lu Yang Wang Jia-Ji Li Chun-Mei Zhang Rong Wang Zhen-Qiang Yin Qing-Yu Cai Henan Key laboratory of quantum Information and Cryptography SSF IEUZhengzhou 450000China Institute of quantum Information and Technology Nanjing University of Posts and TelecommunicationsNanjing 210003China Department of Physics University of Hong KongHong Kong 999077China Key laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China School of Information and communication Engineering Hainan UniversityHaikou 570228China

In a perfect quantum key distribution(QKD)protocol,quantum states should be prepared and measured with mutually unbiased bases(MUBs).However,in a practical QKD system,quantum states are generally prepared and measured with imperfect MUBs using imperfect devices,possibly reducing the secret key rate and transmission *** analyze the security of a QKD system with imperfect MUBs,we propose virtual MUBs to characterize the quantum channel against collective attack,and analyze the corresponding secret key rate under imperfect state preparation and measurement *** generally,we apply the advantage distillation method for analyzing the security of QKD with imperfect MUBs,where the error tolerance and transmission distance can be sharply *** analysis method can be applied to benchmark and standardize a practical QKD system,elucidating the security analysis of different QKD protocols with imperfect devices.

关键词： quantum key distribution mutually unbiased bases advantage distillation

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Atomic transport dynamics in crossed optical dipole trap

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Chinese Physics B 2024年第7期33卷 293-301页

作者：彭鹏张正熙樊耀塬殷国玲毛德凯陈徐宗熊炜周小计 State Key laboratory of Advanced Optical communication System and Network School of ElectronicsPeking UniversityBeijing 100871China Institute of Carbon-based Thin Film Electronics Peking UniversityTaiyuan 030012China State Key laboratory of quantum Optics and quantum Optics Devices Institute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China

We study the dynamical evolution of cold atoms in crossed optical dipole trap theoretically and experimentally. The atomic transport process is accompanied by two competitive kinds of physical mechanics, atomic loading and atomic *** loading process normally is negligible in the evaporative cooling experiment on the ground, while it is significant in preparation of ultra-cold atoms in the space station. Normally, the atomic loading process is much weaker than the atomic loss process, and the atomic number in the central region of the trap decreases monotonically, as reported in previous research. However, when the atomic loading process is comparable to the atomic loss process, the atomic number in the central region of the trap will initially increase to a maximum value and then slowly decrease, and we have observed the phenomenon first. The increase of atomic number in the central region of the trap shows the presence of the loading process, and this will be significant especially under microgravity conditions. We build a theoretical model to analyze the competitive relationship, which coincides with the experimental results well. Furthermore, we have also given the predicted evolutionary behaviors under different conditions. This research provides a solid foundation for further understanding of the atomic transport process in traps. The analysis of loading process is of significant importance for preparation of ultra-cold atoms in a crossed optical dipole trap under microgravity conditions.

关键词： cold atom crossed optical dipole trap transport process

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