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Experimental review on Majorana zero-modes in hybrid nanowires

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arXiv 2020年

作者： Fu, Ji-Bang Li, Bin Zhang, Xin-Fang Yu, Guang-Zheng Huang, Guang-Yao Deng, Ming-Tang Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computer Science and Technology NUDT Changsha410073 China

As the condensed matter analog of Majorana fermion, the Majorana zero-mode is well known as a building block of fault-tolerant topological quantum computing. This review focuses on the recent progress of Majorana experiments, especially experiments about semiconductor-superconductor hybrid devices. We first sketch Majorana zero-mode formation from a bottom-up view, which is more suitable for beginners and experimentalists. Then, we survey the status of zero-energy state signatures reported recently, from zero-energy conductance peaks, the oscillations, the quantization, and the interactions with extra degrees of freedom. We also give prospects of future experiments for advancing one-dimensional semiconductor nanowire-superconductor hybrid materials and devices. Copyright © 2020, The Authors. All rights reserved.

关键词： Hybrid materials

Improving performance for simulating complex fluids on massively parallel computers by component loop-unrolling and communication hiding 22

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Improving performance for simulating complex fluids on massi...

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： Guo, Xiao-Wei Li, Chao Li, Wei Cao, Yu Liu, Yi Zhao, Ran Zhang, Sen Yang, Canqun Institute for Quantum Information State Key Laboratory of High Performance Computing Colloege of Computer National University of Defense Technology Changsha Hunan China Colloege of Meteorology and Oceanology National University of Defense Technology Changsha Hunan China Press and Communication Center of the Pla Technical Support Office of Network Department Beijing China

ISBN: (纸本)9781728176499

Due to the complex geometry and physical models of real-world engineering applications, the parallel performance of the mainstream computational fluid dynamics(CFD) codes is unsatisfactory. For complex fluids, an extra stress tensor governed by constitutive equations including nine components brings much more amount of computations. This paper focused on optimizing the most compute-intensive part of a simulation for complex fluids: The iterative linear solver for solving multicomponent equations. Based on the most widely used opensource CFD code OpenFOAM, we unrolled the component loops and replaced the blocking collective MPI calls to non-blocking communications. After operation rescheduling between the loops, the collective communications could be partly overlapped by the computations. Taking the preconditioned conjugate gradient (PCG) algorithm for instance, we presented the complete loop unrolled algorithm for solving multi-component equations. The numerical experiments showed 8.0%29.0% simulation time reduction for a demonstrative case with 2 million cells on 642048 cores. It is worth noting that the approach proposed in this paper is a high-level scheduling algorithm and could be used in combination with other intra-component optimization algorithms, *** pipelined CG methods. © 2020 IEEE.

关键词： Constitutive equations

FILT: Optimizing KV-Embedded File Systems through Flat Indexing

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FILT: Optimizing KV-Embedded File Systems through Flat Index...

International Conference on Distributed computing Systems

作者： Chen Chen Tongliang Deng Jian Zhang Yanliang Zou Xiaomin Zhu Shu Yin School of Information Science and Technology ShanghaiTech University China State Key Laboratory of High Performance Computing China National University of Defense Technology China

ISBN: (数字)9781728170022

ISBN: (纸本)9781728170039

The effectiveness of applying key-value store mechanisms to manage metadata of file systems has been demonstrated recently. However, traditional indirect metadata indexing schemes are not in concert with modern key-value data structures, which could degrade the performance of a KV-embedded file system due to the overhead of hierarchical path queries. In this paper, we propose FILT, a proof-of-concept file system middleware that can solve this problem by employing flat indexing. FILT exploits the benefits of both flat indexing and LSM-tree structure to eliminate redundant path lookups. Our extensive performance evaluation studies show that FILT can offer up to 5.8x performance gain compared with sophisticated local file systems.

关键词： File systems Metadata performance gain Data structures Throughput Middleware Indexing

Bulk superconductivity in pressurized trilayer nickelate Pr4Ni3O10 single crystals

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arXiv 2025年

作者： Zhang, Enkang Peng, Di Zhu, Yinghao Chen, Lixing Cui, Bingkun Wang, Xingya Wang, Wenbin Zeng, Qiaoshi Zhao, Jun State Key Laboratory of Surface Physics Department of Physics Fudan University Shanghai200433 China Shanghai Research Center for Quantum Sciences Shanghai201315 China Shanghai201203 China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research Institute Chinese Academy of Sciences Shanghai201204 China Institute of Nanoelectronics and Quantum Computing Fudan University Shanghai200433 China Center for High Pressure Science and Technology Advanced Research Shanghai201203 China Hefei National Laboratory Hefei230088 China

The discovery of superconductivity in pressurized bilayer and trilayer nickelates has generated significant interest. However, their superconducting properties are often dependent on sample quality and pressure conditions, complicating the interpretation of the underlying physics. Finding new systems with optimized bulk superconducting properties is therefore important for advancing our understanding of these materials. Unlike cupates, where trilayer compounds typically exhibit the highest transition temperature (Tc), the bilayer nickelate La3Ni2O7 has thus far outperformed the trilayer La4Ni3O10 in reported Tc. Whether the trilayer nickelates have achieved the optimal Tc remains unclear, with various scenarios suggesting different possibilities. Here, we report the discovery of bulk superconductivity in pressurized Pr4Ni3O10 single crystals, achieving a maximum onset Tc of 40.5 K at 80.1 GPa, significantly exceeding the 30 K observed in La4Ni3O10. The bulk nature of superconductivity is confirmed by zero resistance and a strong diamagnetic response below Tc with a superconducting volume fraction exceeding 80%. These findings establish trilayer nickelates as genuine bulk high-temperature superconductors, provide new insights into the mechanisms driving superconductivity, and point to a promising route toward further enhancing superconducting properties in nickelates. © 2025, CC BY-NC-ND.

关键词： Single crystals

A geometric proximal gradient method for sparse least squares regression with probabilistic simplex constraint

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arXiv 2021年

作者： Xiao, Guiyun Bai, Zheng-Jian School of Mathematical Sciences Xiamen University Xiamen361005 China School of Mathematical Sciences Fujian Provincial Key Laboratory on Mathematical Modeling & High Performance Scientific Computing Xiamen University Xiamen361005 China

In this paper, we consider the sparse least squares regression problem with probabilistic simplex constraint. Due to the probabilistic simplex constraint, one could not apply the l1 regularization to the considered regression model. To find a sparse solution, we reformulate the least squares regression problem as a nonconvex and nonsmooth l1 regularized minimization problem over the unit sphere. Then we propose a geometric proximal gradient method for solving the regularized problem, where the explicit expression of the global solution to every involved subproblem is obtained. The global convergence of the proposed method is established under some mild assumptions. Some numerical results are reported to illustrate the effectiveness of the proposed *** Codes 65K05, 90C25, 90C26 Copyright © 2021, The Authors. All rights reserved.

关键词： Gradient methods

Randomized regularized extended Kaczmarz algorithms for tensor recovery

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arXiv 2021年

作者： Du, Kui Sun, Xiao-Hui School of Mathematical Sciences Fujian Provincial Key Laboratory of Mathematical Modeling and High Performance Scientific Computing Xiamen University Xiamen361005 China School of Mathematical Sciences Xiamen University Xiamen361005 China

Randomized regularized Kaczmarz algorithms have recently been proposed to solve tensor recovery models with consistent linear measurements. In this work, we propose a novel algorithm based on the randomized extended Kaczmarz algorithm (which converges linearly in expectation to the unique minimum norm least squares solution of a linear system) for tensor recovery models with inconsistent linear measurements. We prove the linear convergence in expectation of our algorithm. Numerical experiments on a tensor least squares problem and a sparse tensor recovery problem are given to illustrate the theoretical *** Codes 65F10, 68W20, 90C25, 15A69 Copyright © 2021, The Authors. All rights reserved.

关键词： Linear systems

Security boundaries of an optical-power limiter for protecting quantum-key-distribution systems

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Physical Review Applied 2024年第1期21卷 014026-014026页

作者： Qingquan Peng Binwu Gao Konstantin Zaitsev Dongyang Wang Jiangfang Ding Yingwen Liu Qin Liao Ying Guo Anqi Huang Junjie Wu Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha 410073 China School of Automation Central South University Changsha 410083 China China Greatwall Research Institute China Greatwall Technology Group Co. Ltd. Shenzhen 518057 China Russian Quantum Center Skolkovo Moscow 121205 Russia NTI Center for Quantum Communications National University of Science and Technology MISiS Moscow 119049 Russia Vigo Quantum Communication Center University of Vigo 36310 Vigo Spain Escuela de Ingeniería de Telecomunicación Department of Signal Theory and Communications University of Vigo 36310 Vigo Spain atlanTTic Research Center University of Vigo 36310 Vigo Spain College of Computer Science and Electronic Engineering Hunan University Changsha 410082 China School of Computer Science Beijing University of Posts and Telecommunications Beijing 100876 China

Unauthorized light injection has always been a vital threat to the practical security of a quantum-key-distribution (QKD) system. An optical-power limiter (OPL) based on the thermo-optical defocusing effect has been proposed and implemented, limiting the injected hacking light. As a hardware countermeasure, the performance of the OPL under various light-injection attacks will be tested to clarify the security boundary before it is widely deployed. To investigate the security boundary of the OPL in quantum cryptography, we comprehensively test and analyze the behavior of the OPL under continuous-wave (cw) light-injection attacks and pulse-illumination attacks with pulse repetition rates of 0.5 Hz, 40 MHz, and 1 GHz. The test results illuminate the security boundary of the OPL, which allows one to properly employ the OPL in use cases. The methodology of testing and analysis proposed here is applicable to other power-limitation components in a QKD system.

关键词： Optical quantum information processing Photonics Quantum communication Quantum cryptography Devices

Magnetic-field-induced nonlinear transport in HfTe5

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arXiv 2023年

作者： Zhang, Cheng Yang, Jinshan Yan, Zhongbo Yuan, Xiang Liu, Yanwen Zhao, Minhao Suslov, Alexey Zhang, Jinglei Pi, Li Wang, Zhong Xiu, Faxian Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai200433 China Shanghai Qi Zhi Institute Shanghai200232 China State Key Laboratory of Surface Physics Department of Physics Fudan University Shanghai200433 China Zhangjiang Fudan International Innovation Center Fudan University Shanghai201210 China State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai200050 China School of Physics Sun Yat-Sen University Guangzhou510275 China State Key Laboratory of Precision Spectroscopy East China Normal University Shanghai200062 China National High Magnetic Field Laboratory TallahasseeFL32310 United States Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory of the Chinese Academy of Sciences Hefei230031 China Institute for Advanced Study Tsinghua University Beijing100084 China Collaborative Innovation Center of Quantum Matter Beijing100871 China Shanghai Research Center for Quantum Sciences Shanghai201315 China

The interplay of electron correlations and topological phases gives rise to various exotic phenomena including fractionalization, excitonic instability, and axionic excitation. Recently-discovered transition-metal pentatellurides can reach the ultra-quantum limit in low magnetic fields and serve as good candidates for achieving such a combination. Here, we report evidences of density wave and metal-insulator transition in HfTe5 induced by intense magnetic fields. Using the nonlinear transport technique, we detect a distinct nonlinear conduction behavior in the longitudinal resistivity within the a-c plane, corresponding to the formation of a density wave induced by magnetic fields. In high fields, the onset of the nonlinear conduction in the Hall resistivity indicates an impurity-pinned magnetic freeze-out as the possible origin of the insulating behavior. These frozen electrons can be gradually re-activated into mobile states above a threshold electric field. These experimental evidences call for further investigations into the underlying mechanism for the bulk quantum Hall effect and field-induced phase transtions in pentatellurides. © 2023, CC BY.

关键词： Quantum chemistry

The Dual Role of Interlayer Crosslinks Leads to an Abnormal Behavior of Interlayer Thermal Resistance in Multilayer Graphene

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SSRN

SSRN 2022年

作者： Chen, Yan Wan, Jing Chen, Yang Qin, Huasong Liu, Yilun Pei, Qing-Xiang Zhang, Yong-Wei Laboratory for Multiscale Mechanics and Medical Science SV LAB School of Aerospace Xi'an Jiaotong University Xi'An710049 China School of Mechanics and Safety Engineering Zhengzhou University Zhengzhou450001 China Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai University Shanghai200072 China Institute of High Performance Computing A*STAR Singapore138632 Singapore State Key Laboratory for Strength and Vibration of Mechanical Structures China

Understanding and controlling the interlayer thermal resistance (ITR) are crucial to the cross-plane thermal transport in multilayer graphene (MLG). Using non-equilibrium molecular dynamics simulations, we show that the ITR of MLG can be effectively tuned by in-plane defects, sp 2 and sp 3 C-C bond crosslinks. Specifically, with the increase of the in-plane defect density, the ITR initially increases sharply and then almost saturates;while with the increase of the crosslink density, the ITR initially also increases sharply, then peaks and subsequently decreases rapidly to a level that can be even lower than that of pristine MLG. The underlying mechanism for this unexpected variation of ITR with crosslink density is explored through the analyses of the phonon density of states (DOS) and spectral transmission function. It was found that the crosslinks play a dual role: the crosslink-generated in-plane defect enhances phonon scattering and leads to an increase in the ITR, while the interlayer bonding gives rise to a fast phonon transmission pathway and decreases the ITR. An effective medium approximation (EMA) model was proposed to describe the dual role of the crosslinks. This work provides new insight into the thermal transport behavior of crosslinks, which is useful for modulating the cross-plane thermal transport of MLG for the thermal management of MLG-based nanodevices. © 2022, The Authors. All rights reserved.

关键词： Molecular dynamics