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ARPES investigation of the electronic structure and its evolution in magnetic topological insulator MnBi2+2nTe4+3n family

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National Science Review 2024年第2期11卷 81-93页

作者： Runzhe Xu Lixuan Xu Zhongkai Liu Lexian Yang Yulin Chen state Key Laboratory of Low Dimensional Quantum Physics Department of PhysicsTsinghua University School of Physical Science and Technology Shanghai Tech University and CAS-Shanghai Science Research Center Shanghai Tech Laboratory for Topological Physics Frontier Science center for Quantum information Collaborative Innovation center of Quantum Matter Department of Physics Clarendon LaboratoryUniversity of Oxford

In the past 5 years,there has been significant research interest in the intrinsic magnetic topological insulator family compounds MnBi2+2nTe4+3n（where n=0,1,2…）.In particular,exfoliated thin films of MnBi2Te4have led to numerous experimental breakthroughs,such as the quantum anomalous Hall effect,axion insulator phase and high-Chern number quantum Hall effect without Landau ***,despite extensive efforts,the energy gap of the topological surface states due to exchange magnetic coupling,which is a key feature of the characteristic band structure of the system,remains experimentally *** electronic structure measured by using angle-resolved photoemission （ARPES） shows significant deviation from ab initio prediction and scanning tunneling spectroscopy measurements,making it challenging to understand the transport results based on the electronic *** paper reviews the measurements of the band structure of MnBi2+2nTe4+3nmagnetic topological insulators using ARPES,focusing on the evolution of their electronic structures with temperature,surface and bulk doping and film *** aim of the review is to construct a unified picture of the electronic structure of MnBi2+2nTe4+3ncompounds and explore possible control of their topological properties.

关键词： magnetic topological insulator MnBi2Te4 electronic structure angle-resolved photoemission spectroscopy

Stimulated Brillouin interaction between guided phonons and photons in a lithium niobate waveguide

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 173-175页

作者： Yuan-Hao Yang Jia-Qi Wang Zheng-Xu Zhu Xin-Biao Xu Qiang Zhang Juanjuan Lu Yu Zeng Chun-Hua Dong Luyan Sun Guang-Can Guo Chang-Ling Zou CAS Key Laboratory of Quantum information University of Science and Technology of ChinaHefei 230026China CAS center for Excellence in Quantum information and Quantum Physics University of Science and Technology of ChinaHefei 230026China Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China School of information Science and Technology ShanghaiTech UniversityShanghai 201210China center for Quantum information Institute for Interdisciplinary Information SciencesTsinghua UniversityBeijing 100084China

The Brillouin scattering is one of the strongest nonlinear optical effects in dielectrics[1].In particular,the backward Brillouin scattering(BBS)provides an efficient method to achieve low-noise optical gain for active photonics[2]and the coherent interconnects between 10 GHz phonons and photons[3].However,previous studies on BBS are primarily limited to the unconfined phonons[1]or phonon confined in suspended structures[4-6].

关键词： scattering waveguide Brillouin

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In situ calibrated angle between the quantization axis and the propagating direction of the light field for trapping neutral atoms

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Chinese Physics B 2024年第2期33卷 318-323页

作者：郭瑞军何晓东盛诚王坤鹏许鹏刘敏王谨孙晓红曾勇詹明生 Henan Key Laboratory of Laser and Optoelectronic information National Center for International Joint Research of Electronic Materials and SystemsSchool of Electrical and Information EngineeringZhengzhou UniversityZhengzhou 450001China state Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China

The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique relies on applying a bias magnetic field precisely parallel to the wave vector of a circularly polarized trapping laser field. However, due to the presence of the vector light shift experienced by the trapped atoms, it is challenging to precisely define a parallel magnetic field, especially at a low bias magnetic field strength, for the magic-intensity trapping of85Rb qubits. In this work, we present a method to calibrate the angle between the bias magnetic field and the trapping laser field with the compensating magnetic fields in the other two directions orthogonal to the bias magnetic field direction. Experimentally, with a constantdepth trap and a fixed bias magnetic field, we measure the respective resonant frequencies of the atomic qubits in a linearly polarized trap and a circularly polarized one via the conventional microwave Rabi spectra with different compensating magnetic fields and obtain the corresponding total magnetic fields via the respective resonant frequencies using the Breit–Rabi formula. With known total magnetic fields, the angle is a function of the other two compensating magnetic ***, the projection value of the angle on either of the directions orthogonal to the bias magnetic field direction can be reduced to 0(4)° by applying specific compensating magnetic fields. The measurement error is mainly attributed to the fluctuation of atomic temperature. Moreover, it also demonstrates that, even for a small angle, the effect is strong enough to cause large decoherence of Rabi oscillation in a magic-intensity trap. Although the compensation method demonstrated here is explored for the magic-intensity trapping technique, it can be applied to a variety of similar precision measurements with trapped neutral atoms.

关键词： quantization axis trapping laser angle compensating magnetic fields

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Fully distributed dynamic event-triggered formation-containment tracking for multiagent systems with multiple types of disturbances

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Science China(information Sciences) 2024年第1期67卷 168-186页

作者： Weihua LI Huaguang ZHANG Juan ZHANG Rui WANG College of information Science and Engineering Northeastern University state Key Laboratory of Synthetical Automation for Process Industries Northeastern University

This paper is dedicated to addressing the time-varying output formation-containment tracking(TVOFCT) problem for heterogeneous linear multiagent systems(MASs) with multiple types of disturbances under directed communication *** agents are divided into tracking leaders,formation leaders,and *** the output space,the formation leaders are required to form an expected geometric formation while tracking the tracking leader,and the followers are required to enter the convex hull spanned by formation ***,a disturbance observer is designed to observe the disturbance with deterministic ***,by combining adaptive technology with event-triggered technology,an independent fully distributed dynamic event-triggered(FDDET) compensator is designed to estimate the state of the tracking *** main advantages of this compensator lie in the following three aspects:(1) the adaptive weight does not increase unboundedly;(2) the interval time between events is expanded;(3) the design does not rely on any global *** to the design of this compensator,an independent FDDET convex hull observer is further designed to observe the convex hull spanned by formation ***,based on the designed disturbance observer,compensator,and convex hull observer,the adaptive disturbance rejection control input which can make the MASs achieve TVOFCT is ***,a numerical simulation is provided to clearly verify the validity of the theoretical results.

关键词： formation-containment tracking disturbance rejection multiagent systems fully distributed control dynamic event-triggered control

Multi-UAV Collaborative Edge Computing Algorithm for Joint Task Offloading and Channel Resource Allocation

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Journal of Communications and information Networks 2024年第2期9卷 137-150页

作者： Yuting Wei Sheng Wu Zhe Ji Zhigang Yu Chunxiao Jiang Linling Kuang School of information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China China Academy of Electronics and information Technology Beijing 100041China Beijing National Research center for information Science and Technology Tsinghua Space CenterTsinghua UniversityBeijing 100084China

Unmanned aerial vehicle (UAV)-based edge computing is an emerging technology that provides fast task processing for a wider area. To address the issues of limited computation resource of a single UAV and finite communication resource in multi-UAV networks, this paper joints consideration of task offloading and wireless channel allocation on a collaborative multi-UAV computing network, where a high altitude platform station (HAPS)is adopted as the relay device for communication between UAV clusters consisting of UAV cluster heads (ch-UAVs) and mission UAVs (m-UAVs). We propose an algorithm, jointing task offloading and wireless channel allocation to maximize the average service success rate (ASSR)of a period time. In particular,the simulated annealing(SA)algorithm with random perturbations is used for optimal channel allocation,aiming to reduce interference and minimize transmission delay.A multi-agent deep deterministic policy gradient (MADDPG) is proposed to get the best task offloading strategy. Simulation results demonstrate the effectiveness of the SA algorithm in channel allocation. Meanwhile,when jointly considering computation and channel resources,the proposed scheme effectively enhances the ASSR in comparison to other benchmark algorithms.

关键词： UAV-based edge computing multi-UAV collaboration joint task offloading and wireless channel allocation simulated annealing(SA)algorithm multi-agent deep deterministic policy gradient(MADDPG)

Simulations of superconducting quantum gates by digital flux tuner for qubits

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Chinese Physics B 2024年第7期33卷 210-222页

作者：耿霄何楷泳刘建设陈炜 Laboratory of Superconducting Quantum information Processing School of Integrated CircuitsTsinghua UniversityBeijing 100084China Beijing Innovation center for Future Chips Tsinghua UniversityBeijing 100084China Beijing National Research center for information Science and Technology Beijing 100084China26

The interconnection bottleneck caused by limitations of cable number, inner space and cooling power of dilution refrigerators has been an outstanding challenge for building scalable superconducting quantum computers with the increasing number of qubits in quantum processors. To surmount such an obstacle, it is desirable to integrate qubits with quantum–classical interface(QCI) circuits based on rapid single flux quantum(RSFQ) circuits. In this work, a digital flux tuner for qubits(DFTQ) is proposed for manipulating flux of qubits as a crucial part of the interface circuit. A schematic diagram of the DFTQ is presented, consisting of a coarse tuning unit and a fine-tuning unit for providing magnetic flux with different precision to qubits. The method of using DFTQ to provide flux for gate operations is discussed from the optimization of circuit design and input signal. To verify the effectiveness of the method, simulations of a single DFTQ and quantum gates including a Z gate and an iSWAP gate with DFTQs are performed for flux-tunable transmons. The quantum process tomography corresponding to the two gates is also carried out to analyze the sources of gate error. The results of tomography show that the gate fidelities independent of the initial states of the Z gate and the iSWAP gate are 99.935% and 99.676%,respectively. With DFTQs inside, the QCI would be a powerful tool for building large-scale quantum computers.

关键词： quantum computation superconducting electronics quantum control

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Combo Packet:An Encryption Traffic Classification Method Based on Contextual information

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Computers, Materials & Continua 2024年第4期79卷 1223-1243页

作者： Yuancong Chai Yuefei Zhu Wei Lin Ding Li state Key Laboratory of Mathematical Engineering and Advanced Computing Information Engineering UniversityZhengzhou450001China

With the increasing proportion of encrypted traffic in cyberspace, the classification of encrypted traffic has becomea core key technology in network supervision. In recent years, many different solutions have emerged in this *** methods identify and classify traffic by extracting spatiotemporal characteristics of data flows or byte-levelfeatures of packets. However, due to changes in data transmission mediums, such as fiber optics and satellites,temporal features can exhibit significant variations due to changes in communication links and transmissionquality. Additionally, partial spatial features can change due to reasons like data reordering and *** with these challenges, identifying encrypted traffic solely based on packet byte-level features is significantlydifficult. To address this, we propose a universal packet-level encrypted traffic identification method, ComboPacket. This method utilizes convolutional neural networks to extract deep features of the current packet andits contextual information and employs spatial and channel attention mechanisms to select and locate effectivefeatures. Experimental data shows that Combo Packet can effectively distinguish between encrypted traffic servicecategories (e.g., File Transfer Protocol, FTP, and Peer-to-Peer, P2P) and encrypted traffic application categories (e.g.,BitTorrent and Skype). Validated on the ISCX VPN-non VPN dataset, it achieves classification accuracies of 97.0%and 97.1% for service and application categories, respectively. It also provides shorter training times and higherrecognition speeds. The performance and recognition capabilities of Combo Packet are significantly superior tothe existing classification methods mentioned.

关键词： Encrypted traffic classification packet-level convolutional neural network attention mechanisms

Multivariate Time Series Anomaly Detection Based on Spatial-Temporal Network and Transformer in Industrial Internet of Things

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Computers, Materials & Continua 2024年第8期80卷 2815-2837页

作者： Mengmeng Zhao Haipeng Peng Lixiang Li Yeqing Ren information Security center State Key Laboratory ofNetworking and Switching TechnologyBeijing University of Posts and TelecommunicationsBeijing100876China National Engineering Laboratory for Disaster Backup and Recovery Beijing University of Posts and TelecommunicationsBeijing100876China Department of information Science and Engineering Zaozhuang UniversityZaozhuang277160China

In the Industrial Internet of Things(IIoT),sensors generate time series data to reflect the working *** the systems are attacked,timely identification of outliers in time series is critical to ensure *** many anomaly detection methods have been proposed,the temporal correlation of the time series over the same sensor and the state(spatial)correlation between different sensors are rarely considered simultaneously in these *** to the superior capability of Transformer in learning time series *** paper proposes a time series anomaly detection method based on a spatial-temporal network and an improved ***,the methods based on graph neural networks typically include a graph structure learning module and an anomaly detection module,which are ***,in the initial phase of training,since neither of the modules has reached an optimal state,their performance may influence each *** scenario makes the end-to-end training approach hard to effectively direct the learning trajectory of each *** interdependence between the modules,coupled with the initial instability,may cause the model to find it hard to find the optimal solution during the training process,resulting in unsatisfactory *** introduce an adaptive graph structure learning method to obtain the optimal model parameters and graph *** on two publicly available datasets demonstrate that the proposed method attains higher anomaly detection results than other methods.

关键词： Multivariate time series anomaly detection spatial-temporal network Transformer

Designing novel adaptive dynamic event-triggered protocols for uncertain multi-agent systems

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Science China(information Sciences) 2024年第1期67卷 310-311页

作者： Bin CHENG Bin HE College of Electronics and information Engineering Tongji University Frontiers Science center for Intelligent Autonomous Systems

Multi-agent systems (MASs) have garnered widespread attention and have been investigated by numerous researchers in recent years, primarily due to their broad applications in industry, transportation, agriculture, and astronomy. While studying the cooperative control of MASs, numerous researchers place emphasis on reducing the frequency of communication among neighboring agents.

关键词： Directed graphs