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Bright 547-dimensional Hilbert-space entangled resource in 28-pair modes biphoton frequency comb from a reconfigurable silicon microring resonator

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Chinese Physics B 2022年第2期31卷 129-134页

作者： Qilin Zheng Jiacheng Liu Chao Wu Shichuan Xue Pingyu Zhu Yang Wang Xinyao Yu Miaomiao Yu Mingtang Deng Junjie Wu Ping Xu Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer.National University of Defense TechnologyChangsha 410073China College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410013China National Laboratory of Solid State Microstructures and School of Physics Nanjing University.Nanjing 210093China

high-dimensional entanglement provides valuable resources for quantum technologies,including quantum communication,quantum optical coherence tomography,and quantum *** a high brightness and dimensional entanglement source has significant *** we utilize a tunable asymmetric Mach–Zehnder interferometer coupled silicon microring resonator with 100 GHz free spectral range to achieve this *** the strategy of the tunable coupler,the dynamical and extensive tuning range of quality factors of the microring can be obtained,and then the biphoton pair generation rate can be *** selecting and characterizing 28 pairs from a more than 30-pair modes biphoton frequency comb,we obtain a Schmidt number of at least 23.4 and on-chip pair generation rate of 19.9 MHz/m W;under a low on-chip pump power,which corresponds to 547 dimensions Hilbert space in frequency *** results will prompt the wide applications of quantum frequency comb and boost the further large density and scalable on-chip quantum information processing.

关键词： silicon microring resonator quantum entanglement biphoton frequency comb

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Degenerate polarization entangled photon source based on a single Ti-diffusion lithium niobate waveguide in a polarization Sagnac interferometer

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Chinese Physics B 2023年第8期32卷 69-73页

作者：孙宇孙昌伟周唯杨然端家晨龚彦晓徐平祝世宁 National Laboratory of Solid State Microstructures and School of Physics Nanjing UniversityNanjing 210093China NanZhi Institude of Advanced Optoelectronic Integration Nanjing 210018China Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer Science and TechnologyNational University of Defense TechnologyChangsha 410073China

Combining a Ti-diffusion periodically poled lithium niobate(PPLN)waveguide with a Sagnac interferometer,two opposite directions type-II spontaneous parametric down conversions(SPDC)occur coherently and yield a high brightness,high stability polarization entanglement *** source produces degenerate photon pairs at 1540.4 nm with a brightness of B=(1.36±0.03)×10^(6) pairs/(s·nm·m W).We perform quantum state tomography to reconstruct the density matrix of the output state and obtain a fidelity of F=0.983±*** high brightness and phase stability of our waveguide source enable a wide range of quantum information experiments operating at a low pump power as well as hold the advantage in mass production which can promote the practical applications of quantum technologies.

关键词： polarization entanglement source Sagnac interferometer quantum information lithium niobate waveguide

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Credit assignment for trained neural networks based on Koopman operator theory

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Frontiers of Computer Science 2024年第1期18卷 251-253页

作者： Zhen LIANG Changyuan ZHAO Wanwei LIU Bai XUE Wenjing YANG Zhengbin PANG Institute for Quantum Information&State Key Laboratory of High Performance Computing National University of Defense TechnologyChangsha 410000China Institute of Software Chinese Academy of SciencesBeijing 100190China College of Computer Science and Technology National University of Defense TechnologyChangsha 410000China

1 Introduction Artificial neural networks(ANNs,also NNs)have recently emerged as leading candidate models for deep learning,popularly used in various areas[1–3].Behind the enormous success,ANNs are generally with complicated structures,there being an intricate data flow through multiple linear or nonlinear components between the input layer and the output ***,it is pressing to evaluate how much a specific component contributes to the final output,termed the Credit Assignment Problem(CAP)[4]in this paper.

关键词： layer assignment operator

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The 20-nm Skyrmion Generated at Room Temperature by Spin-Orbit Torques

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Chinese Physics Letters 2022年第1期39卷 40-45页

作者： Jiahao Liu Zidong Wang Teng Xu Hengan Zhou Le Zhao Soong-Guen Je Mi-Young Im Liang Fang Wanjun Jiang State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084China Frontier Science Center for Quantum Information Tsinghua UniversityBeijing 100084China Institute for Quantum Information&State Key Laboratory of High Performance Computing College of ComputerNational University of Defense TechnologyChangsha 410073China Center for X-ray Optics Lawrence Berkeley National LaboratoryCyclotron RoadBerkeleyCA 94720USA Department of Physics Chonnam National UniversityGwangju61186Republic of Korea

The discovery of magnetic skyrmions provides a promising pathway for developing functional spintronic memory and logic devices. Towards the future high-density memory application, nanoscale skyrmions with miniaturized diameters, ideally down to 20 nm are required. Using x-ray magnetic circular dichroism transmission microscopy,nanoscale skyrmions are observed in the [Pt/Co/Ir]15 multilayer at room temperature. In particular, small skyrmions with minimum diameters approaching 20 nm could be generated by the current-induced spin-orbit torques. Through implementing material specific parameters, the dynamic process of skyrmion generation is further investigated by performing micromagnetic simulations. According to the simulation results, we find that both the tube-like Neel-type skyrmions and the bobber-like Neel-type skyrmions can be electrically generated. In particular, the size of the bobber-like Neel-type skyrmions can be effectively reduced by the spin-orbit torques,which leads to the formation of 20 nm Neel-type skyrmions. Our findings could be important for understanding the formation dynamics of nanoscale Neel-type spin textures, skyrmions and bobber in particular, which could also be useful for promoting nanoscale skyrmionic memories and logic devices.

关键词： temperature diameters approaching

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Electron–phonon coupling in topological insulator Bi_2Se_3 thin films with different substrates

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Chinese Optics Letters 2019年第2期17卷 21-24页

作者： Tian Jiang Runlin Miao Jie Zhao Zhongjie Xu Tong Zhou Ke Wei Jie You Xin Zheng Zhenyu Wang Xiang’ai Cheng College of Advanced Interdisciplinary Studies National University of Defense Technology State Key Laboratory of High Performance Computing College of Computer National University of Defense Technology Interdisciplinary Center of Quantum Information National University of Defense Technology National Institute of Defense Technology Innovation Academy of Military Sciences PLA China

Broadband transient reflectivity traces were measured for Bi_2 Se_3 thin films with various substrates via a 400 nm pump–white-light-probe setup. We have verified the existence of a second Dirac surface state in Bi_2 Se_3 and qualitatively located it by properly analyzing the traces acquired at different probe wavelengths. Referring to the band structure of Bi_2 Se_3, the relaxation mechanisms for photo-excited electrons with different energies are also revealed and studied. Our results show a second rise of the transient reflection signal at the time scale of several picoseconds. The types of substrate can also significantly affect the dynamics of the rising signal. This phenomenon is attributed to the effect of lattice heating and coherent phonon processes. The mechanism study in this work will benefit the fabrication of high-performance photonic devices based on topological insulators.

关键词： phonon coupling insulator films

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quantum algorithm and experimental demonstration for the subset sum problem

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Science China(information Sciences) 2022年第8期65卷 261-274页

作者： Qilin ZHENG Pingyu ZHU Shichuan XUE Yang WANG Chao WU Xinyao YU Miaomiao YU Yingwen LIU Mingtang DENG Junjie WU Ping XU Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer Science and TechnologyNational University of Defense Technology

To solve the subset sum problem, a well-known nondeterministic polynomial-time complete problem that is widely used in encryption and resource scheduling, we propose a feasible quantum algorithm that utilizes fewer qubits to encode and achieves quadratic speedup. Specifically, this algorithm combines an amplitude amplification algorithm with quantum phase estimation, and requires n + t + 1 qubits and O(2(0.5+o(1))n) operations to obtain the solution, where n is the number of elements, and t is the number of qubits used to store the eigenvalues. To verify the performance of the algorithm, we simulate the algorithm with the online quantum simulator of IBM named ibmq simulator using Qiskit and then run it on two IBM quantum computers called ibmq santiago and ibmq bogota. The experimental results indicate that compared with the brute force algorithm, the proposed algorithm results in quadratic acceleration for the problem of a set S with four elements and two subsets whose sum equals target w. Using the iterator twice, we obtain success probabilities of 0.940 ± 0.004, 0.751 ± 0.040, and 0.665 ± 0.060 on the simulator, ibmq santiago, and ibmq bogota, respectively, and the fidelity between the theoretical and experimental quantum states is calculated to be 0.944 ± 0.002, 0.753 ± 0.017, and 0.657 ± 0.028, respectively. If the error rates of the experimental quantum logic gates can be reduced, the success probabilities of the proposed algorithm on real quantum devices can be further improved.

关键词： quantum algorithm subset sum quadratic speedup encryption algorithm complexity

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Developing a proxy application for an industrial unstructured CFD software: preliminary results 29

Developing a proxy application for an industrial unstructure...

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29th IEEE International Conference on Parallel and Distributed Systems, ICPADS 2023

作者： Wang, Qingsong Xu, Chuanfu Zhang, Jian Deng, Liang Dai, Zhe Qiu, Haozhong Dai, Weixi Lin, Yongzhen Ding, Yue Che, Yonggang National University of Defense Technology Institute for Quantum Information State Key Laboratory of High Performance Computing Changsha China China Aerodynamic Research and Development Center Mianyang China

ISBN: (纸本)9798350330717

As programming models and architectures evolve in the exa-scale era, porting large-scale HPC applications are becoming increasingly difficult and expensive. In HPC community, mini-apps are often developed to mimic real-world applications, and it offers an easy way to benchmark new HPC platforms. In this paper, we design and implement a mini-app MiniFS as a proxy for an industry-level unstructured Computational Fluid Dynamics (CFD) software FlowStar. The main purpose of MiniFS is to evaluate different shared memory approaches on emerging multi/many-core architectures, because data conflicts and data dependencies in unstructured CFD pose tough challenges for shared memory parallelization. Results show that our mini-app can represent the performance characteristic of the original application. However, the existing approaches are unscalable on modern multi/many-cores. It is imperative to develop novel scalable shared memory approaches for unstructured CFD. © 2023 IEEE.

关键词： mini-app shared memory unstructured CFD

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Qualitative and Quantitative Model Checking Against Recurrent Neural Networks

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Journal of Computer Science & Technology 2024年第6期39卷 1292-1311页

作者： Zhen Liang Wan-Wei Liu Fu Song Bai Xue Wen-Jing Yang Ji Wang Zheng-Bin Pang Institute for Quantum Information&State Key Laboratory of High Performance Computing College of Computer Science and TechnologyNational University of Defense TechnologyChangsha 410073China College of Computer Science and Technology National University of Defense TechnologyChangsha 410073China School of Information Science and Technology ShanghaiTech UniversityShanghai 201210China Institute of Software Chinese Academy of SciencesBeijing 100190China

Recurrent neural networks (RNNs) have been heavily used in applications relying on sequence data such as time series and natural languages. As a matter of fact, their behaviors lack rigorous quality assurance due to the black-box nature of deep learning. It is an urgent and challenging task to formally reason about the behaviors of RNNs. To this end, we first present an extension of linear-time temporal logic to reason about properties with respect to RNNs, such as local robustness, reachability, and some temporal properties. Based on the proposed logic, we formalize the verification obligation as a Hoare-like triple, from both qualitative and quantitative perspectives. The former concerns whether all the outputs resulting from the inputs fulfilling the pre-condition satisfy the post-condition, whereas the latter is to compute the probability that the post-condition is satisfied on the premise that the inputs fulfill the pre-condition. To tackle these problems, we develop a systematic verification framework, mainly based on polyhedron propagation, dimension-preserving abstraction, and the Monte Carlo sampling. We also implement our algorithm with a prototype tool and conduct experiments to demonstrate its feasibility and efficiency.

关键词： recurrent neural network model checking temporal logic qualitative/quantitative verification

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ANF: Attention-Based Noise Filtering Strategy for Unsupervised Few-Shot Classification 18th

ANF: Attention-Based Noise Filtering Strategy for Unsupervis...

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18th Pacific Rim International Conference on Artificial Intelligence, PRICAI 2021

作者： Ni, Guangsen Zhang, Hongguang Zhao, Jing Xu, Liyang Yang, Wenjing Lan, Long Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer National University of Defense Technology Changsha410073 China Systems Engineering Institute AMS Beijing China

ISBN: (纸本)9783030893699

How to learn concepts from few-shot samples remains an open challenge in the deep learning era. The previous meta-learning methods require a large number of annotated samples in the training phase, which still contributes to high manual-labeling costs. In this paper, we propose a unsupervised few-shot learning framework and pointed out that negative queue constructed via randomly sampling contains many false-negative samples (noise), which has negative impacts on the model’s generalized performance especially when only few samples are available. Specially, we propose an Attention-based Noise Filtering (ANF) strategy to make momentum contrastive loss more applicable to few-shot learning scenario. In addition, we also propose a dynamic momentum update method, which can greatly improve the classification accuracy. Our evaluations demonstrate state-of-the-art unsupervised few-shot learning performance, which is comparable to supervised baseline models. © 2021, Springer Nature Switzerland AG.

关键词： Computer vision

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DSGA: Distractor-Suppressing Graph Attention for Multi-object Tracking 8

DSGA: Distractor-Suppressing Graph Attention for Multi-objec...

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8th International Conference on Robotics and Artificial Intelligence, ICRAI 2022

作者： Gao, Guangjie Gao, Yan Xu, Liyang Tan, Huibin Tang, Yuhua Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha China Chinese Institute of Electronics Beijing China

ISBN: (纸本)9781450397544

Multiple object tracking (MOT) methods based on single object tracking are of great interest because of their ability to balance efficiency and performance on the strength of the localization capability of single-target tracking. However, most of the single object tracking methods only distinguish foreground and background. They are susceptible to the influence of similar interfering objects during localization, while in multiple object tracking scenarios, there are more interfering objects and the influence is more severe. Therefore, we propose a Distractor-Suppressing Graph Attention (DSGA) to learn more discriminative attention by reducing the influence of distractors on learning attention weight features. Furthermore, DSGA is embedded into the basic MOT framework "SiamMOT" formed as DSGA-SiamMOT and applied to multiple object tracking to verify its effectiveness. We conduct experiments on the MOT Challenge benchmark with "public detection", and obtain MOTA 66.65%, IDF1 62.2% accuracy on the MOT17 dataset with 14fps. © 2022 Association for computing Machinery.

关键词： Target tracking

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