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

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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

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

quantum state tomography from observable time traces in closed quantum systems

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Control Theory and Technology 2024年第2期22卷 222-234页

作者： Shuixin Xiao Yuanlong Wang Qi Yu Jun Zhang Daoyi Dong Ian R.Petersen University of Michigan–Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong UniversityShanghai200240China School of Engineering The Australian National UniversityCanberraACT2601Australia Key Laboratory of systems and Control Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing100190China centre for quantum Computation and Communication Technology(Australian Research Council) Centre for Quantum DynamicsGriffith UniversityBrisbaneQLD4111Australia School of Engineering and Technology University of New South WalesCanberraACT2600Australia

The task to estimate all the parameters of an unknown quantum state, also called quantum state tomography, is essential for characterizing and controlling quantum systems. In this paper, we utilize observable time traces to identify the initial quantum state of a closed quantum system, based on the state space approach in the control theory. In the informationally complete scenario, we show that with a linear regression estimation (LRE), the mean squared error (MSE) scales as , where N is the resource number. In the informationally incomplete scenario, we introduce regularization LRE to perform the state tomography task. We employ PBH test to demonstrate that closed quantum systems with only one observable are informationally incomplete and propose using observables, where d is the dimension of the quantum state, for informational completeness. Numerical examples demonstrate the effectiveness of our method.

关键词： quantum state tomography Time trace quantum system identification

Single crystal growth and characterization of 166-type magnetic kagome metals

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Chinese Physics B 2024年第9期33卷 145-150页

作者： Huangyu Wu Jinjin Liu Yongkai Li Peng Zhu Liu Yang Fuhong Chen Deng Hu Zhiwei Wang centre for quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(MOE)School of PhysicsBeijing Institute of TechnologyBeijing 100081China Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic systems Beijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Zhuhai 519000China Material Science Center Yangtze Delta Region Academy of Beijing Institute of TechnologyJiaxing 314011China

Kagome magnets were predicted to be a good platform to investigate correlated topology band structure,Chern quantum phase,and geometrical frustration due to their unique lattice *** we reported single crystal growth of 166-type kagome magnetic materials,including HfMn_(6)Sn_(6),ZrMn_(6)Sn_(6),GdMn_(6)Sn_(6)and GdV_(6)Sn_(6),by using the flux method with Sn as the *** them,HfMn_(6)Sn_(6)and ZrMn_(6)Sn_(6)single crystals were grown for the first time.X-ray diffraction measurements reveal that all four samples crystallize in HfFe6Ge6-type hexagonal structure with space group P6/*** samples show metallic behavior from temperature dependence of resistivity measurements,and the dominant carrier is hole,except for GdV6Sn6 which is electron *** samples have magnetic order with different transition temperatures,HfMn_(6)Sn_(6),ZrMn_(6)Sn_(6)and GdV_(6)Sn_(6)are antiferromagnetic with TN of 541 K,466 K and 4 K respectively,while GdMn_(6)Sn_(6)is ferrimagnetic with the critical temperature of about 470 *** study will enrich the research platform of magnetic kagome materials and help explore the novel quantum phenomena in these interesting *** dataset of specific crystal structure parameters for HfMn_(6)Sn_(6)are available in Science Data Bank,with the link.

关键词： kagome metal single crystal growth crystal structure physical property

Scaling laws governing the elastic properties of 3D graphenes

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Science China(Technological Sciences) 2024年第6期67卷 1748-1756页

作者： LI Ming LU Guo YU HaoDong LI MengLei ZHENG FaWei centre for quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(MOE)School of PhysicsBeijing Institute of TechnologyBeijing100081China Beijing Key Lab of Nanophotonics&Ultrafine Optoelectronic systems School of PhysicsBeijing Institute of TechnologyBeijing100081China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing100088China Department of Physics Capital Normal UniversityBeijing100048China

In this study,we comprehensively investigated the scaling law for elastic properties of three-dimensional honeycomb-like graphenes(3D graphenes)using hybrid neural network potential-based molecular dynamics simulations and theoretical *** elastic constants were obtained as functions of honeycomb hole size,denoted by the graphene wall length *** five independent elastic constants in the large-L limit are proportional to L^(-1).The associated coefficients are combinations of elastic constants of two-dimensional ***-order terms including L^(-2)and L^(-3)emerge for finite L *** have three origins,the distorted areas close to the joint lines of 3D graphenes,the variation in solid angles between graphene plates,and the bending distortion of graphene ***,the chirality becomes essential with decreasing L because the joint line structures are different between the armchair and zigzag-type 3D *** findings provide insights into the elastic properties of graphene-based superstructures and can be used for further studies on graphene-based materials.

关键词： scaling law neural network elastic properties 3D graphene

Spin Resolved Zero-Line Modes in Minimally Twisted Bilayer Graphene from Exchange Field and Gate Voltage

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Chinese Physics Letters 2024年第7期41卷 111-116页

作者： Sanyi You Jiaqi An Zhenhua Qiao International centre for quantum Design of Functional Materials CAS Key Laboratory of Strongly Coupled Quantum Matter Physicsand Department of PhysicsUniversity of Science and Technology of ChinaHefei 230026China Hefei National Laboratory University of Science and Technology of ChinaHefei 230088China

The reliance on spin-orbit coupling or strong magnetic fields has always posed significant challenges for the mass production and even laboratory realization of most topological materials. Valley-based topological zero-line modes have attracted widespread attention due to their substantial advantage of being initially realizable with just an external electric field. However, the uncontrollable nature of electrode alignment and precise fabrication has greatly hindered the advancement in this field. By utilizing minimally twisted bilayer graphene and introducing exchange fields from magnetic substrates, we successfully realize a spin-resolved, electrode-free topological zeroline mode. Further integration of electrodes that do not require alignment considerations significantly enhances the tunability of the system's band structure. Our approach offers a promising new support for the dazzling potential of topological zero-line mode in the realm of low-energy-consumption electronics.

关键词： structure field topological

quantum dense coding with gravitational cat states

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Communications in Theoretical Physics 2024年第3期76卷 84-90页

作者： Saeed Haddadi Mehrdad Ghominejad Artur Czerwinski Faculty of Physics Semnan UniversityP.O.Box 35195-363SemnanIran centre for quantum Optical Technologies Centre of New TechnologiesUniversity of WarsawBanacha 2c02-097 WarszawaPoland

A protocol of quantum dense coding with gravitational cat states is *** explore the effects of temperature and system parameters on dense coding capacity and provide an efficient strategy to preserve the quantum advantage of dense coding for these *** results may open new opportunities for secure communication and insights into the fundamental nature of gravity in the context of quantum information processing.

关键词： quantum dense coding gravitational cat states quantum advantage

Microscopic growth mechanism and edge states of monolayer 1T'-MoTe2

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Chinese Physics B 2024年第4期33卷 474-480页

作者：赵海鹏刘隐杨胜国林陈昉陈明星 Kai Braun 罗心仪李思宇潘安练王笑 Key Laboratory for Micro-Nano Physics and Technology of Hunan Province School of Physics and ElectronicsCollege of Materials Science and Engineering Hunan University Key Laboratory of Low-Dimensional quantum Structures and quantum Control of Ministry of Education Synergetic Innovation Centre for Quantum Effects and Applications (SICQEA) Hunan Normal University State Key Laboratory of Powder Metallurgy Central South University Institute of Physical and Theoretical Chemistry and LISA+ University of Tübingen

Transition metal ditellurides（TMTDs） have versatile physical properties,including non-trivial topology,Weyl semimetal states and unique spin *** growth of high-quality and large-scale monolayer TMTDs with preferred crystal phases is crucial for their ***,we demonstrate the epitaxial growth of 1T'-MoTe2on Au（111）and graphitized silicon carbide（Gr/SiC） by molecular beam epitaxy（MBE）.We investigate the morphology of the grown1T'-MoTe2at the atomic level by scanning tunnelling microscopy（STM） and reveal the corresponding microscopic growth *** is found that the unique ordered Te structures preferentially deposited on Au（111） regulate the growth of monolayer single crystal 1T'-MoTe2,while the Mo clusters were preferentially deposited on the Gr/SiC substrate,which impedes the ordered growth of monolayer *** confirm that the size of single crystal 1T'-MoTe2grown on Au（111）is nearly two orders of magnitude larger than that on Gr/*** scanning tunnelling spectroscopy（STS）,we observe that the STS spectrum of the monolayer 1T'-MoTe2nano-island at the edge is different from that at the interior,which exhibits enhanced conductivity.

关键词： 1T′-MoTe2 microscopic growth mechanism scanning tunneling microscopy/spectroscopy (STM/S) transition metal ditellurides

Towards growth of pure AB-stacked bilayer graphene single crystals

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Nano Research 2024年第5期17卷 4616-4621页

作者： Xiaowen Zhang Tao Zhou Yunlong Ren Zuo Feng Ruixi Qiao Qinghe Wang Bin Wang Jinxia Bai Muhong Wu Zhilie Tang Xu Zhou Kaihui Liu Xiaozhi Xu Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum MaterialsSchool of PhysicsSouth China Normal UniversityGuangzhou 510006China Guangdong-Hong Kong Joint Laboratory of quantum Matter School of PhysicsSouth China Normal UniversityGuangzhou 510006China Physical Science and Engineering Division King Abdullah University of Science and TechnologyThuwal 23955–6900Saudi Arabia State Key Laboratory for Mesoscopic Physics Frontiers Science Center for Nano-optoelectronicsSchool of PhysicsPeking UniversityBeijing 100871China Institute for Frontier Science Nanjing University of Aeronautics and AstronauticsNanjing 210094China International centre for quantum Materials Collaborative Innovation Centre of Quantum MatterPeking UniversityBeijing 100871China Songshan Lake Materials Laboratory Institute of PhysicsChinese Academy of SciencesDongguan 523808China

Given its intriguing band structure and unique tunable bandgap,AB-stacked bilayer graphene has great potentials in the applications of high-end electronics,optoelectronics and *** epitaxial growth of AB-stacked single-crystal bilayer graphene films requires a strict AB-stacked lattice,identical orientations and seamless stitching of bilayer graphene ***,the particles inevitably present on the metal surface that produced during high temperature growth would induce random orientations,twisted stacking islands,and uncontrollable multilayers,which is a great challenge to ***,we propose a heat-resisting-box assisted strategy to produce nearly pure AB-stacked bilayer graphene single-crystal films on Cu/Ni(111)*** our technique,the particles on the Cu/Ni(111)surface are effectively eliminated,which greatly minimizes the occurrence of randomly twisted islands and uncontrollable *** as-grown AB-stacked bilayer graphene films show>99%alignment and>99%AB stacking *** work provides a promising method towards the growth of pure AB-stacked bilayer graphene single crystals and would accelerate its device applications.

关键词： bilayer graphene AB stacking uniform growth heat-resisting box