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arXiv 2025年

作者： Cao, Hanyan Zhao, Shoukuan Feng, Dongyang Shen, Zisong Yan, Haisheng Su, Tang Sun, Weijie Xu, Huikai Pan, Feng Yu, Haifeng Zhang, Pan CAS Key Laboratory for Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100049 China Beijing Academy of Quantum Information Sciences Beijing100193 China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced Study UCAS Hangzhou310024 China Centre for Quantum Technologies National University of Singapore 117543 Singapore Science Mathematics and Technology Cluster Singapore University of Technology and Design 8 Somapah Road 487372 Singapore Hefei National Laboratory Hefei230088 China

Repetition code forms a fundamental basis for quantum error correction experiments. To date, it stands as the sole code that has achieved large distances and extremely low error rates. Its applications span the spectrum of evaluating hardware limitations, pinpointing hardware defects, and detecting rare events. However, current methods for decoding repetition codes under circuit level noise are suboptimal, leading to inaccurate error correction thresholds and introducing additional errors in event detection. In this work, we establish that repetition code under circuit level noise has an exact solution, and we propose an optimal maximum likelihood decoding algorithm called Planar . The algorithm is based on the exact solution of the spin glass partition function on planar graphs and has polynomial computational complexity. Through extensive numerical experiments, we demonstrate that our algorithm uncovers the exact threshold for depolarizing noise and realistic superconductor SI1000 noise. Furthermore, we apply our method to analyze data from recent quantum memory experiments conducted by Google Quantum AI, revealing that part of the error floor was attributed to the decoding algorithm used by Google. Finally, we implemented the repetition code quantum memory on superconducting systems with a 72-qubit quantum chip lacking reset gates, demonstrating that even with an unknown error model, the proposed algorithm achieves a significantly lower logical error rate than the matching-based algorithm. © 2025, CC BY.

关键词： Spin glass

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The role of plasma beta in global coronal models: Bringing balance back to the force

arXiv

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arXiv 2023年

作者： Brchnelova, Michaela Kuźma, Blażej Zhang, Fan Lani, Andrea Poedts, Stefaan Centre for Mathematical Plasma Astrophysics KU Leuven Celestijnenlaan 200B Leuven3001 Belgium Shenzhen Key Laboratory of Numerical Prediction for Space Storm Institute of Space Science and Applied Technology Harbin Institute of Technology Shenzhen518055 China Key Laboratory of Solar Activity and Space Weather National Space Science Center Chinese Academy of Sciences Beijing100190 China Institute of Physics University of Maria Curie-Sklodowska ul. Radziszewskiego 10 Lublin20-031 Poland

Context. COolfluid COrona uNstrUcTured (COCONUT) is a global coronal magnetohydrodynamic (MHD) model that has been recently developed and will soon be integrated into the ESA Virtual Space Weather Modelling Centre (VSWMC). In order to achieve robustness and fast convergence to steady-state for numerical simulations with COCONUT, several assumptions and simplifications have been made during its development, such as prescribing filtered photospheric magnetic maps for representing the magnetic field conditions in the lower corona. This filtering leads to smoothing and lower magnetic field values at the inner boundary (i.e., the solar surface), resulting in an unrealistically high plasma β (more than 1 in a large portion of the domain). Aims. In this paper, we examine the effects of prescribing such filtered/smoothed magnetograms in global coronal simulations and formulate a method for achieving more realistic plasma β values and improving the resolution of electromagnetic features without losing computational performance. Methods. We make use of the newly developed COCONUT solver to demonstrate the effects of the highly pre-processed magnetic maps set at the inner boundary and the resulting high plasma β on the features in the computational domain. Then, in our new approach, we shift the inner boundary to 2 R☉ from the original 1.01 R☉ and preserve the prescribed highly filtered magnetic map. With the shifted boundary, naturally, the boundary density and pressure are also adjusted to better represent the considered physical location. This effectively reduces the prescribed plasma β and leads to a more realistic setup. The method is applied on a magnetic dipole, a minimum (2008) and a maximum (2012) solar activity case, to demonstrate its effects. Results. The results obtained with the proposed approach show significant improvements in the resolved density and radial velocity profiles, and far more realistic values of the plasma β at the boundary and inside the computat

关键词： Magnetohydrodynamics

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Integrating Neural Networks and Tensor Networks for Computing Free Energy

arXiv

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arXiv 2025年

作者： Cao, Hanyan Wang, Yijia Pan, Feng Zhang, Pan CAS Key Laboratory for Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100049 China Centre for Quantum Technologies National University of Singapore 117543 Singapore Science Mathematics and Technology Cluster Singapore University of Technology and Design 8 Somapah Road 487372 Singapore School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced Study UCAS Hangzhou310024 China International Centre for Theoretical Physics Asia-Pacific Hangzhou Beijing China

Computing free energy is a fundamental problem in statistical physics. Recently, two distinct methods have been developed and have demonstrated remarkable success: the tensor-network-based contraction method and the neural-network-based variational method. Tensor networks are accurate, but their application is often limited to low-dimensional systems due to the high computational complexity in high-dimensional systems. The neural network method applies to systems with general topology. However, as a variational method, it is not as accurate as tensor networks. In this work, we propose an integrated approach, tensor-network-based variational autoregressive networks (TNVAN), that leverages the strengths of both tensor networks and neural networks: combining the variational autoregressive neural network’s ability to compute an upper bound on free energy and perform unbiased sampling from the variational distribution with the tensor network’s power to accurately compute the partition function for small sub-systems, resulting in a robust method for precisely estimating free energy. To evaluate the proposed approach, we conducted numerical experiments on spin glass systems with various topologies, including two-dimensional lattices, fully connected graphs, and random graphs. Our numerical results demonstrate the superior accuracy of our method compared to existing approaches. In particular, it effectively handles systems with long-range interactions and leverages GPU efficiency without requiring singular value decomposition, indicating great potential in tackling statistical mechanics problems and simulating high-dimensional complex systems through both tensor networks and neural networks. © 2025, CC BY.

关键词： Statistical mechanics

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Application of improved genetic ant colony optimization in radar resource interference allocation

Application of improved genetic ant colony optimization in r...

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IET International Radar Conference (IET IRC 2020)

作者： Y. Liao W. Guo L. Hu Harbin Engineering University Information and Communication Engineering Department Harbin China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

Under the condition of limited interference resources, how to maximize the benefits of multiple jammers interfering with multiple radars has become a research hotspot. This paper has designed a reasonable interference evaluation method. Aiming at the disadvantages of genetic algorithm and ant colony optimization, made some improvements, and combined genetic methods and ant colony optimization, besides, a new crossover and mutation method based on constraints is proposed, which overcomes the shortcomings of invalid iteration of genetic algorithm and easy to fall into local optimal solution of ant colony optimization. Through simulation analysis, the fused algorithm can reach the optimal value within a short number of iterations, improving the utilization efficiency of the jammer.

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The Predictability of Ocean Environments that Contributed to the 2020/21 Extreme Cold Events in China:2020/21 La Niña and 2020 Arctic Sea Ice Loss

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Advances in Atmospheric sciences 2022年第4期39卷 658-675页

作者： Fei ZHENG Ji-Ping LIU Xiang-Hui FANG Mi-Rong SONG Chao-Yuan YANG Yuan YUAN Ke-Xin LI Ji WANG Jiang ZHU International Center for Climate and Environment Science(ICCES) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science&TechnologyNanjing 210044China Department of Atmospheric and Environmental Sciences University at Albany State University of New YorkAlbanyNY 12222USA Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China School of Atmospheric Sciences Sun Yat-sen UniversityZhuhai 519082China National Climate Center Beijing 100081China University of Chinese Academy of Sciences Beijing 100049China Beijing Municipal Climate Center Beijing 100089China

Several consecutive extreme cold events impacted China during the first half of winter 2020/21,breaking the low-temperature records in many *** to make accurate climate predictions of extreme cold events is still an urgent *** synergistic effect of the warm Arctic and cold tropical Pacific has been demonstrated to intensify the intrusions of cold air from polar regions into middle-high latitudes,further influencing the cold conditions in ***,climate models failed to predict these two ocean environments at expected lead *** seasonal climate forecasts only predicted the 2020/21 La Niña after the signal had already become apparent and significantly underestimated the observed Arctic sea ice loss in autumn 2020 with a 1-2 month *** this work,the corresponding physical factors that may help improve the accuracy of seasonal climate predictions are further *** the 2020/21 La Niña prediction,through sensitivity experiments involving different atmospheric-oceanic initial conditions,the predominant southeasterly wind anomalies over the equatorial Pacific in spring of 2020 are diagnosed to play an irreplaceable role in triggering this cold event.A reasonable inclusion of atmospheric surface winds into the initialization will help the model predict La Niña development from the early spring of *** predicting the Arctic sea ice loss in autumn 2020,an anomalously cyclonic circulation from the central Arctic Ocean predicted by the model,which swept abnormally hot air over Siberia into the Arctic Ocean,is recognized as an important contributor to successfully predicting the minimum Arctic sea ice extent.

关键词： extreme cold event predictability La Niña Arctic sea ice loss

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Mechanically Beam-steering of Horn Antenna Using Non-uniform Flexible Meta-Surface

Mechanically Beam-steering of Horn Antenna Using Non-uniform...

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International Conference on Computer and Communications (ICCC)

作者： Zhiye Jiang Pei Zheng Yuwei Qiu Hailiang Zhu Chenyu Ding Gao Wei National Key Laboratory of Science and Technology on Test Physics &Numerical Mathematics Beijing China School of Electronics and Information Northwestern Polytechnical University Xi'an Shaanxi China

ISBN: (数字)9781728186351

ISBN: (纸本)9781728186368

Research on mechanically beam-steering of horn antenna using non-uniform meta-surface is presented in this paper. After optimizing the layout of quasi-I-shaped unit cell, we designed a flexible bi-layer meta-surface that can bring a main beam deflection of 40°. When the meta-surface is sliding along the long side of horn antenna, the main beam can be steered accordingly in a range of ±40°. A mechanically radiation reconfigurable antenna is thus achieved by a simple structure. Sliding of the meta-surface relative to the horn can be realized by a motor-driven conveyor belt when the prototype is fabricated in the following research.

关键词： Geometry Beam steering Horn antennas Conferences Layout Prototypes Bandwidth

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Optimization and Performance Modeling of Stencil Computations on ARM Architectures 22

Optimization and Performance Modeling of Stencil Computation...

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22nd IEEE International Conference on High Performance Computing and Communications, 18th IEEE International Conference on Smart City and 6th IEEE International Conference on Data science and Systems, HPCC-SmartCity-DSS 2020

作者： Zhang, Kaifang Su, Huayou Zhang, Peng Dou, Yong National University of Defense Technology National Key Laboratory for Parallel and Distribution Processing Changsha China Caep Software Center for High Performance Numerical Simulation Beijing China Institute of Applied Physics and Computational Mathematics Beijing China

ISBN: (纸本)9781728176499

Stencil Computation has long been an omnipresent kernel of a wide range of scientific and engineering applications. There is much work investigating the stencil performance on x86 processors and accelerators such as GPU. Meanwhile, ARM processors for HPC have been highlighted more and more with Fugaku of Japan becoming the first number one system on the TOP-500 list. In this paper, we focus on modeling and optimizing the performance of stencil computation on ARM architectures. Specifically, we proposed a performance model for stencil computation based on tiling optimization to guide the optimal configuration of tiling parameters for good cache reuse. We validate the proposed model with the Performance Monitor Unit (PMU) provided by the ARM processor. Experimental results show that the prediction error of the execution time can be lower to 1.37%. Furthermore, we can achieve a maximum of 1.26 \times speedup compared to the naive implementation according to the optimization parameters provided from the model. © 2020 IEEE.

关键词： ARM processors

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Adaptive extended Kalman filter and point ahead angle prediction in the detection of gravitational waves in space

arXiv

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arXiv 2024年

作者： Yang, Jinke Xie, Yong Tang, Wenlin Liang, Xindong Zhang, Liang Cui, Zhao Wang, Xue Li, Haojie Jia, Jianjun Lau, Yun Kau Shanghai Institute of Technical Physics Chinese Academy of Sciences Shanghai200083 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory of Electronics and Information Technology for Space System National Space Science Center Chinese Academy of Sciences Beijing100190 China Hangzhou Institute for Advanced Study UCAS Hangzhou310024 China Institute of Applied Mathematics Morningside Center of Mathematics LSSC Academy of Mathematics and System Science Chinese Academy of Sciences 55 Zhongguancun Donglu Beijing100190 China

In the detection of gravitational waves in space, during the science phase of the mission, the point ahead angle mechanism (PAAM) serves to steer a laser beam to compensate for the angle generated by the relative motion of the two spacecrafts (SCs) during the approximately 10 seconds of flight time a laser beam will take from one SC to reach a distant SC of three million kilometers away. The common practice for pointing stability control of a laser beam is to first do a coarse tracking by the PAAM to steer a laser beam to compensate for the relative motion between two SCs, to be followed by a fine pointing stability control. In the present work, by exploiting the near-circular orbit structure of individual SC in the triangular constellation, the feasibility of inserting an adaptive Kalman filter (AEKF) into the PAAM control loop is investigated. By adopting a colored measurement noise model that closely resembles the prospective on orbit situation, numerical simulation suggests that the dynamic range of the PAAM may be reduced to the level of nanoradians using the prediction of the pointing head angle (PAA) by the AEKF. This will cut down on the TTL coupling noise and the position noise budget allocated to the PAAM. This in turn reduces the dynamic range of the fine pointing control and leaves room to improve its accuracy, thereby offers the prospect of reduction of the position noise budget allocated to the laser pointing instability as a whole. Copyright © 2024, The Authors. All rights reserved.

关键词： Laser beams

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Interpretable machine-learning strategy for soft-magnetic property and thermal stability in Fe-based metallic glasses

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npj Computational Materials 2020年第1期6卷 1-9页

作者： Lu, Zhichao Chen, Xin Liu, Xiongjun Lin, Deye Wu, Yuan Zhang, Yibo Wang, Hui Jiang, Suihe Li, Hongxiang Wang, Xianzhen Lu, Zhaoping Beijing Advanced Innovation Center for Materials Genome Engineering State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing100083 China Institute of Applied Physics and Computational Mathematics Beijing100088 China Software Center for High Performance Numerical Simulation Chinese Academy of Engineering Physics Beijing100088 China Institute for Advanced Materials and Technology University of Science and Technology Beijing Beijing100083 China

Fe-based metallic glasses (MGs) have been extensively investigated due to their unique properties, especially the outstanding soft-magnetic properties. However, conventional design of soft-magnetic Fe-based MGs is heavily relied on "trial and error" experiments, and thus difficult to balance the saturation flux density (Bs) and thermal stability due to the strong interplay between the glass formation and magnetic interaction. Herein, we report an eXtreme Gradient Boosting (XGBoost) machine-learning (ML) model for developing advanced Fe-based MGs with a decent combination of Bs and thermal stability. While it is an attempt to apply ML for exploring soft-magnetic property and thermal stability, the developed XGBoost model based on the intrinsic elemental properties (i.e., atomic size and electronegativity) can well predict Bs and Tx (the onset crystallization temperature) with an accuracy of 93.0% and 94.3%, respectively. More importantly, we derived the key features that primarily dictate Bs and Tx of Fe-based MGs from the ML model, which enables the revelation of the physical origins underlying the high Bs and thermal stability. As a proof of concept, several Fe-based MGs with high Tx (>800 K) and high Bs (>1.4 T) were successfully developed in terms of the ML model. This work demonstrates that the XGBoost ML approach is interpretable and feasible in the extraction of decisive parameters for properties of Fe-based magnetic MGs, which might allow us to efficiently design high-performance glassy materials. © 2020, The Author(s).

关键词： Thermodynamic stability

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Unified OSTBC-based communication scheme for cooperative space vehicles

Unified OSTBC-based communication scheme for cooperative spa...

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IET International Radar Conference 2018, IRC 2018

作者： Geng, Jian Liu, Hongyan Jin, Wen Yan, Xinfeng Xu, Jin Beijing Institute of Space Long March Vehicle Beijing China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics China

In many spatial cooperative vehicle networks, omni-directional communication is preferred due to its flexibility for networking. In the recent studies, space time code was shown to be an effective approach for improving the performance of the omni-directional communication between space vehicles. This paper studies the unified scheme for the orthogonal space time block code-based transmission between two space vehicles equipped with different numbers of antennas. It is obtained that at most six passive antennas and four RF chains are enough for the typical use. In the proposed scheme, the receiver can perform a unified detection procedure regardless of the actual number of the transmit antennas, which facilitates the practical application. Simulation results validate the proposed scheme in terms of the cumulative distribution function of the received signal-to-noise ratios. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Space time codes

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