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arXiv 2024年

作者： Ruan, Xinhui Wang, Jia-Heng He, Dong Song, Pengtao Li, Shengyong Zhao, Qianchuan Kuang, L.M. Tsai, Jaw-Shen Zou, Chang-Ling Zhang, Jing Zheng, Dongning Astafiev, O.V. Liu, Yu-Xi Peng, Zhihui Department of Automation Tsinghua University Beijing100084 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Department of Physics and Synergetic Innovation Center of Quantum Effects and Applications Hunan Normal University Changsha410081 China School of Integrated Circuits Tsinghua University Beijing100084 China Institute of Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100190 China Center for Quantum Computing RIKEN Saitama351-0198 Japan Graduate School of Science Tokyo University of Science 1-3 Kagurazaka Shinjuku Tokyo162-0825 Japan CAS Key Laboratory of Quantum Information University of Science and Technology of China Hefei Anhui230026 China Hefei National Laboratory Hefei230088 China School of Automation Science and Engineering Xi'an Jiaotong University Xi’an710049 China MOE Key Lab for Intelligent Networks and Network Security Xi'an Jiaotong University Xi’an710049 China Skolkovo Institute of Science and Technology Nobel str. 3 Moscow143026 Russia Moscow Institute of Physics and Technology Institutskiy Pereulok 9 Dolgoprudny141701 Russia Royal Holloway University of London Surrey EghamTW20 0EX United Kingdom

We report an experimental demonstration of resonance fluorescence in a two-level superconducting artificial atom under two driving fields coupled to a detuned cavity. One of the fields is classical and the other is varied from quantum (vacuum fluctuations) to classical one by controlling the photon number inside the cavity. The device consists of a transmon qubit strongly coupled to a one-dimensional transmission line and a coplanar waveguide resonator. We observe a sideband anti-crossing and asymmetry in the emission spectra of the system through a one-dimensional transmission line, which is fundamentally different from the weak coupling case. By changing the photon number inside the cavity, the emission spectrum of our doubly driven system approaches to the case when the atom is driven by two classical bichromatic fields. We also measure the dynamical evolution of the system through the transmission line and study the properties of the first-order correlation function, Rabi oscillations and energy relaxation in the system. The study of resonance fluorescence from an atom driven by two fields promotes understanding decoherence in superconducting quantum circuits and may find applications in superconducting quantum computing and quantum networks. Copyright © 2024, The Authors. All rights reserved.

关键词： Electric lines

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A diffuse-interface lattice Boltzmann method for thermal particulate flows with Dirichlet boundary conditions

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Physics of Fluids 2025年第6期37卷

作者： Liu, Jiao Liu, Xi Chai, Zhenhua School of Mathematics and Computer Science Nanchang University Jiangxi Nanchang330031 China School of Mathematics and Statistics Huazhong University of Science and Technology Wuhan430074 China Institute of Interdisciplinary Research for Mathematics and Applied Science Huazhong University of Science and Technology Wuhan430074 China Hubei Key Laboratory of Engineering Modeling and Scientific Computing Huazhong University of Science and Technology Wuhan430074 China The State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan430074 China

The lattice Boltzmann method has been widely used to study thermal particulate flows that are usually observed in both nature and engineering, while how to efficiently and accurately treat the fluid-solid boundary conditions is still an important and not well-resolved issue. In this paper, a diffuse-interface lattice Boltzmann method (DI-LBM) is developed for complex thermal particulate flows with Dirichlet boundary conditions. Unlike the previous works where the fluid-solid boundary is treated as a sharp interface, the fluid-solid boundary in the DI-LBM is implemented as a diffuse interface such that the physical variables and transport coefficients in the fluid and solid regions are varied smoothly. To depict the diffuse interface, a smooth function is introduced, and simultaneously, an additional source term is added in the evolution equation to reflect the effect of Dirichlet boundary condition imposed on the fluid-solid boundary. The present method is also tested by several classical problems, and the numerical results show that the DI-LBM is not only of second-order convergence rate in space, but also efficient in the study of complex thermal particulate flows. © 2025 Author(s).

关键词： Kinetic theory of gases

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Sentence segmentation for classical Chinese based on LSTM with radical embedding

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The Journal of China Universities of Posts and Telecommunications 2019年第2期26卷 1-8页

作者： Han Xu Wang Hongsu Zhang Sanqian Fu Qunchao Liu Jun School of software Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China Key Laboratory of Trustworthy Distributed Computing and Service (BUPT)Ministry of EducationBeijing 100876China The Key Laboratory of Rich-Media Knowledge Organization and Service of Digital Publishing Content Institute of Scientific and Technical Information of ChinaBeijing 100038China Insitute of Quantitative Social Science Harvard UniversityCambridgeMAUSA Department of statistics Harvard UniversityCambridgeMAUSA

A low-than character feature embedding called radical embedding is proposed,and applied on a long-short term memory(LSTM) model for sentence segmentation of pre-modern Chinese *** dataset includes over 150 classical Chinese books from 3 different dynasties and contains different literary ***-conditional random fields(LSTM-CRF) model is a state-of-the-art method for the sequence labeling *** model adds a component of radical embedding,which leads to improved *** results based on the aforementioned Chinese books demonstrate better accuracy than earlier methods on sentence segmentation,especial in Tang’s epitaph texts(achieving an F1-score of 81.34%).

关键词： LSTM radical embedding sentence segmentation

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SNIG PROPERTY OF MATRIX LOW-RANK FACTORIZATION MODEL

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Journal of Computational Mathematics 2018年第3期36卷 374-390页

作者： Hong Wang Xin Liu Xiaojun Chen Yaxiang Yuan Department of Applied Mathematics The Hong Kong Polytechnic University Hong Kong China State Key Laboratory of Scientific and Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China State Key Laboratory of Scientific and Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

Recently, the matrix factorization model attracts increasing attentions in handling large-scale rank minimization problems, which is essentially a nonconvex minimization problem. Specifically, it is a quadratic least squares problem and consequently a quartic polynomial optimization problem. In this paper, we introduce a concept of the SNIG （＂Second-order Necessary optimality Implies Global optimality＂） condition which stands for the property that any second-order stationary point of the matrix factorization model must be a global minimizer. Some scenarios under which the SNIG condition holds are presented. Furthermore, we illustrate by an example when the SNIG condition may fail.

关键词： Low rank factorization Nonconvex optimization Second-order optimality condition Global minimizer

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Topological structures on saturated sets, optimal orbits and equilibrium states

arXiv

引用

arXiv 2020年

作者： Hou, Xiaobo Tian, Xueting Zhang, Yiwei School of Mathematical Sciences Fudan University Shanghai200433 China School of Mathematics and Statistics Center for Mathematical Sciences Hubei Key Laboratory of Engineering Modeling and Scientific Computing Huazhong University of Sciences and Technology Wuhan430074 China

Pfister and Sullivan proved that if a topological dynamical system (X, T) satisfies almost product property and uniform separation property, then for each nonempty compact subset K of invariant measures, the entropy of saturated set GK satisfies (0.1) hBtop(T, GK) = inf{h(T, µ): µ ∈ K}, where hBtop(T, GK) is Bowen's topological entropy of T on GK, and h(T, µ) is the Kolmogorov-Sinai entropy of µ. In this paper, we investigate topological complexity of GK by replacing Bowen's topological entropy with upper capacity entropy and packing entropy in (0.1) and obtain the following formulas: hUCtop (T, GK) = htop(T, X) and hPtop(T, GK) = sup{h(T, µ): µ ∈ K}, where hUCtop (T, GK) is the upper capacity entropy of T on GK and hPtop(T, GK) is the packing entropy of T on GK. In the proof of these two formulas, uniform separation property is unnecessary. As applications, when (X, T) is a transitive Anosov diffeomorphism on a compact manifold, we show that (1) for any continuous function f, hUCtop (T, Sfop) = htop(T, X) where Sfop is the set of initial values of f-optimal orbits;(2) there exists a Baire generic subset F in the space of continuous functions and an open and dense subset G in the space of Hölder continuous or C1 smooth functions such that for any f ∈ F or f ∈ G, hBtop(T, Sfop) = hPtop(T, Sfop) = 0;(3) for any f ∈ G, hUCtop (T, SfMR) = 0 where SfMR is the set of initial values of measure-recurrent optimal orbits;(4) there exists a dense subset in the space of continuous functions such that for any f in the subset, hBtop(T, Sfop) = hPtop(T, Sfop) > 0. For equilibrium states, we prove that (1) for any continuous function f and equilibrium state µ of f, hUCtop (T, Gµ) = htop(T, X);(2) if f is Hölder continuous and is not cohomologous to a constant, then hBtop(T, Gµ) = hPtop(T, Gµ) fopMSC Codes 37C50, 37B20, 37B05, 37D45, 37C45 © 2020, CC BY.

关键词： Entropy

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Graph denoising with framelet regularizer

arXiv

引用

arXiv 2021年

作者： Zhou, Bingxin Li, Ruikun Zheng, Xuebin Wang, Yu Guang Gao, Junbin The University of Sydney Business School The University of Sydney NSW Australia Institute of Natural Sciences Shanghai Jiao Tong University Shanghai China Institute of Natural Sciences School of Mathematical Sciences Key Laboratory of Scientific and Engineering Computing of Ministry of Education Center for Mathematics of Artificial Intelligence Institute Shanghai Jiao Tong University Shanghai China Shanghai Artificial Intelligence Laboratory Shanghai China School of Mathematics and Statistics The University of New South Wales Australia

As graph data collected from the real world is merely noise-free, a practical representation of graphs should be robust to noise. Existing research usually focuses on feature smoothing but leaves the geometric structure untouched. Furthermore, most work takes L2-norm that pursues a global smoothness, which limits the expressivity of graph neural networks. This paper tailors regularizers for graph data in terms of both feature and structure noises, where the objective function is efficiently solved with the alternating direction method of multipliers (ADMM). The proposed scheme allows to take multiple layers without the concern of over-smoothing, and it guarantees convergence to the optimal solutions. Empirical study proves that our model achieves significantly better performance compared with popular graph convolutions even when the graph is heavily contaminated. © 2021, CC BY.

关键词： Constrained optimization

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Seeking Consensus on Subspaces in Federated Principal Component Analysis

arXiv

引用

arXiv 2020年

作者： Wang, Lei Liu, Xin Zhang, Yin State Key Laboratory of Scientific and Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences University of Chinese Academy of Sciences Beijing China School of Data Science The Chinese University of Hong Kong Shenzhen China

In this paper, we develop an algorithm for federated principal component analysis (PCA) with emphases on both communication efficiency and data privacy. Generally speaking, federated PCA algorithms based on direct adaptations of classic iterative methods, such as simultaneous subspace iterations (SSI), are unable to preserve data privacy, while algorithms based on variable-splitting and consensus-seeking, such as alternating direction methods of multipliers (ADMM), lack in communication-efficiency. In this work, we propose a novel consensus-seeking formulation by equalizing subspaces spanned by splitting variables instead of equalizing variables themselves, thus greatly relaxing feasibility restrictions and allowing much faster convergence. Then we develop an ADMM-like algorithm with several special features to make it practically efficient, including a low-rank multiplier formula and techniques for treating subproblems. We establish that the proposed algorithm can better protect data privacy than classic methods adapted to the federated PCA setting. We derive convergence results, including a worst-case complexity estimate, for the proposed ADMM-like algorithm in the presence of the nonlinear equality constraints. Extensive empirical results are presented to show that the new algorithm, while enhancing data privacy, requires far fewer rounds of communication than existing peer algorithms for federated PCA. Copyright © 2020, The Authors. All rights reserved.

关键词： Principal component analysis

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Liouville-type theorems for steady Navier-Stokes system in a slab with Navier boundary conditions

引用

Journal of Differential Equations 2025年 443卷

作者： Jingwen Han Yun Wang Chunjing Xie School of Mathematical Sciences Shanghai Jiao Tong University 800 Dongchuan Road Shanghai China School of Mathematical Sciences Center for dynamical systems and differential equations Soochow University Suzhou China School of mathematical Sciences Institute of Natural Sciences Ministry of Education Key Laboratory of Scientific and Engineering Computing and CMA-Shanghai Shanghai Jiao Tong University 800 Dongchuan Road Shanghai China

In this paper, the Liouville-type theorems for the steady Navier-Stokes system in a slab supplemented with Navier boundary conditions are investigated. Specifically, we prove that any bounded smooth solution must be zero if either the swirl or radial velocity is axisymmetric, or r u r decays to zero as r tends to infinity. When the velocity is not big in L ∞ -space, the general three-dimensional steady Navier-Stokes flow in a slab with the Navier boundary conditions must be a Poiseuille type flow. The key idea of the proof is to establish the Saint-Venant type estimates that characterize the growth of Dirichlet integral of nontrivial solutions.

关键词：

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Exploring question-specific rewards for generating deep questions

arXiv

引用

arXiv 2020年

作者： Xie, Yuxi Pan, Liangming Wang, Dongzhe Kan, Min-Yen Feng, Yansong Wangxuan Institute of Computer Technology Peking University China NUS Graduate School for Integrative Sciences and Engineering ZhuiYi Technology Singapore School of Computing National University of Singapore Singapore MOE Key Laboratory of Computational Linguistics Peking University China

Recent question generation (QG) approaches often utilize the sequence-to-sequence framework (Seq2Seq) to optimize the log likelihood of ground-truth questions using teacher forcing. However, this training objective is inconsistent with actual question quality, which is often reflected by certain global properties such as whether the question can be answered by the document. As such, we directly optimize for QG-specific objectives via reinforcement learning to improve question quality. We design three different rewards that target to improve the fluency, relevance, and answerability of generated questions. We conduct both automatic and human evaluations in addition to thorough analysis to explore the effect of each QG-specific reward. We find that optimizing on question-specific rewards generally leads to better performance in automatic evaluation metrics. However, only the rewards that correlate well with human judgement (e.g., relevance) lead to real improvement in question quality. Optimizing for the others, especially answerability, introduces incorrect bias to the model, resulting in poor question quality. Our code is publicly available at https://***/YuxiXie/RL-for-Question-Generation. Copyright © 2020, The Authors. All rights reserved.

关键词： Reinforcement learning

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Low-order moments of the velocity gradient in homogeneous compressible turbulence

arXiv

引用

arXiv 2022年

作者： Yang, PingFan Fang, Jian Fang, Le Pumir, Alain Xu, Haitao The State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing100190 China School of Engineering Sciences University of Chinese Academy of Sciences Beijing100049 China Center for Combustion Energy School of Aerospace Engineering Tsinghua University Beijing100084 China Scientific Computing Department STFC Daresbury Laboratory WarringtonWA4 4AD United Kingdom LCS Ecole Centrale de Pékin Beihang University Beijing100191 China Laboratoire de Physique Ecole Normale Supérieure de Lyon CNRS Université de Lyon LyonF-69007 France Max Planck Institute for Dynamics and Self-Organization GöttingenD-37077 Germany

We derive from first principles analytic relations for the second and third order moments of the velocity gradient mij = ∂ui/∂xj in compressible turbulence, which generalize known relations in incompressible flows. These relations, although derived for homogeneous flows, hold approximately for a mixing layer. We also discuss how to apply these relations to determine all the second and third moments of the velocity gradient experimentally. Copyright © 2022, The Authors. All rights reserved.

关键词： Incompressible flow

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