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Publisher’s Note: “Evidences of thermoelectrically driven unidirectional magnetoresistance from a single Weyl ferromagnet Co2MnGa” [APL Mater. 11, 121109 (2023)]

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APL Materials 2024年第1期12卷

作者： Bin Rong Lizhu Ren Yizhe Liu Bo Sun Jiaxin Chen Kie Leong Teo Liang Liu Yumeng Yang b) School of Information Science and Technology ShanghaiTech University Shanghai 201210 China Department of Electrical and Computer Engineering National University of Singapore 117576 Singapore Tsinghua-Berkeley Shenzhen Institute Tsinghua University Shenzhen 518055 China Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education) Tsung-Dao Lee Institute School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China Hefei National Laboratory Hefei 230088 China Shanghai Research Center for Quantum Sciences 99 Xiupu Road Shanghai 201315 China

This article was published online on December 15, 2023, with errors in the author and affiliation lists; several authors were linked to incorrect affiliations.

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Observation of nonreciprocal magneto-optical scattering in nonencapsulated few-layered CrI3

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arXiv 2020年

作者： Guo, Kai Liu, Zhen Hu, Guangwei Shi, Zhongtai Li, Yue Zhang, Linbo Chen, Haiyan Zhang, Li Zhou, Peiheng Lu, Haipeng Lin, Miao-Ling Liu, Sizhao Cheng, Yingchun Liu, Xue Lu Xie, Jianliang Bi, Lei Tan, Ping-Heng Deng, Long jiang Qiu, Cheng-Wei Peng, Bo National Engineering Research Center of Electromagnetic Radiation Control Materials School of Electronic Science and Engineering University of Electronic Science and Technology of China Chengdu611731 China Department of Electrical and Computer Engineering National University of Singapore 117583 Singapore Key Laboratory of Flexible Electronics Institute of Advanced Materials Jiangsu National Synergetic Innovation Center for Advanced Materials Nanjing Tech University Nanjing211816 China State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences P. O. Box 912 Beijing100083 China

"Magneto-optical" effect refers to a rotation of polarization plane, which has been widely studied in traditional ferromagnetic metal and insulator films and scarcely in two-dimensional layered materials. Here we uncover a new nonreciprocal magneto-inelastic light scattering effect in ferromagnetic few-layer CrI3. We observed a rotation of the polarization plane of inelastic light scattering between -20o and +60o that are tunable by an out-of-plane magnetic field from -2.5 to 2.5 T. It is experimentally observed that the degree of polarization can be magnetically manipulated between -20% and 85%. This work raises a new magneto-optical phenomenon and could create opportunities of applying 2D ferromagnetic materials in Raman lasing, topological photonics, and magneto-optical modulator for information transport and storage. © 2020, CC BY-NC-SA.

关键词： Ferromagnetic materials

Regression-based inverter control for decentralized optimal power flow and voltage regulation

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arXiv 2019年

作者： Sondermeijer, Oscar Dobbe, Roel Arnold, Daniel Tomlin, Claire Keviczky, Tamás Department of Electrical Engineering & Computer Sciences UC Berkeley Berkeley United States Department of Mechanical Engineering UC Berkeley Berkeley United States Delft Center for Systems and Control Delft University of Technology Delft Netherlands

Electronic power inverters are capable of quickly delivering reactive power to maintain customer voltages within operating tolerances and to reduce system losses in distribution grids. This paper proposes a systematic and data-driven approach to determine reactive power inverter output as a function of local measurements in a manner that obtains near optimal results. First, we use a network model and historic load and generation data and do optimal power flow to compute globally optimal reactive power injections for all controllable inverters in the network. Subsequently, we use regression to find a function for each inverter that maps its local historical data to an approximation of its optimal reactive power injection. The resulting functions then serve as decentralized controllers in the participating inverters to predict the optimal injection based on a new local measurements. The method achieves near-optimal results when performing voltage- and capacityconstrained loss minimization and voltage flattening, and allows for an efficient volt-VAR optimization (VVO) scheme in which legacy control equipment collaborates with existing inverters to facilitate safe operation of distribution networks with higher levels of distributed generation. Copyright © 2019, The Authors. All rights reserved.

关键词： Acoustic generators

Efficient experimental quantum fingerprinting with wavelength division multiplexing

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arXiv 2020年

作者： Zhong, Xiaoqing Xu, Feihu Lo, Hoi-Kwong Qian, Li Center for Quantum Information and Quantum Control Dept. of Physics University of Toronto TorontoONM5S 1A7 Canada Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics University of Science and Technology of China Hefei230026 China Center for Quantum Information and Quantum Control Dept. of Electrical & Computer Engineering University of Toronto TorontoONM5S 3G4 Canada

Quantum communication complexity studies the efficiency of information communication (that is, the minimum amount of communication required to achieve a certain task) using quantum states. One representative example is quantum fingerprinting, in which the simultaneous message passing model is considered and the minimum amount of communication could be exponentially smaller than the classical fingerprinting protocol. Experimental demonstrations based on a practical quantum fingerprinting protocol where coherent states are used to construct the fingerprints, have successfully shown the superiority of quantum fingerprinting. However, as a consequence of using coherent states, the communication time in this coherent quantum fingerprinting (CQF) protocol is increased. Moreover, the minimum amount of information communicated in these experimental demonstrations is largely limited by the dark counts of the single photon detectors. Here, we propose to enhance the performance of the existing CQF protocol through applying wavelength division multiplexing (WDM) and simultaneous detection of multiple wavelength channels. We show that the new WDM-CQF protocol can potentially reduce the communication time significantly. More importantly, with the same experimental parameters, the amount of communication is much reduced in the new scheme compared with the original CQF protocol. The more wavelength channels are used, the less communication is required by WDM-CQF protocol. We also perform a proof-of-concept experimental demonstration of the new WDM-CQF protocol with 6 wavelength channels. The experimental results further validate that the new scheme with WDM not only beats the classical protocol, but also reduces the amount of communication required by the original CQF protocol by more than half. Copyright © 2020, The Authors. All rights reserved.

关键词： Demonstrations

Small-signal stability of grid-tied inverter networks

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arXiv 2019年

作者： Jafarpour, Saber Purba, Victor Dhople, Sairaj V. Johnson, Brian Bullo, Francesco Department of Mechanical Engineering Center of Control Dynamical Systems and Computation University of California Santa BarbaraCA93106 United States Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55414 United States Department of Electrical Engineering University of Washington SeattleWA98195 United States

This paper considers the small-signal stability of electrical networks composed dominantly of three-phase grid-following inverters. We identify a suitable time-scale decomposition for the inverter dynamics and, using singular perturbation theory, we obtain an analytic sufficient condition for the small-signal stability of the network. In contrast to the alternative of performing an eigenvalue analysis of the full-order network dynamics, our analytic sufficient condition has the benefit of reducing computational complexity and yielding insights on the role of network topology and constitution as well as inverter filter and control parameters on small-signal stability. Our numerical analysis for an inverter network with radial topology validates the approach and illustrates the efficiency of our analytic conditions for designing/monitoring grid-tied inverter networks. Copyright © 2019, The Authors. All rights reserved.

关键词： Eigenvalues and eigenfunctions

Finite-sample analysis of decentralized temporal-difference learning with linear function Approximation

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arXiv 2019年

作者： Sun, Jun Wang, Gang Giannakis, Georgios B. Yang, Qinmin Yang, Zaiyue College of Control Science and Engineering State Key Laboratory of Industrial Control Technology Zhejiang University Hangzhou China Digital Technology Center Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen China

Motivated by the emerging use of multi-agent reinforcement learning (MARL) in engineering applications such as networked robotics, swarming drones, and sensor networks, we investigate the policy evaluation problem in a fully decentralized setting, using temporal-difference (TD) learning with linear function approximation to handle large state spaces in practice. The goal of a group of agents is to collaboratively learn the value function of a given policy from locally private rewards observed in a shared environment, through exchanging local estimates with neighbors. Despite their simplicity and widespread use, our theoretical understanding of such decentralized TD learning algorithms remains limited. Existing results were obtained based on i.i.d. data samples, or by imposing an ‘additional’ projection step to control the ‘gradient’ bias incurred by the Markovian observations. In this paper, we provide a finite-sample analysis of the fully decentralized TD(0) learning under both i.i.d. as well as Markovian samples, and prove that all local estimates converge linearly to a small neighborhood of the optimum. The resultant error bounds are the first of its type—in the sense that they hold under the most practical assumptions —which is made possible by means of a novel multi-step Lyapunov analysis. Copyright © 2019, The Authors. All rights reserved.

关键词： Sampling

Navigation with Multi-obstacle Avoidance Composed of Stochastic Optimal controllers

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Navigation with Multi-obstacle Avoidance Composed of Stochas...

American control Conference (ACC)

作者： Alexey A. Munishkin Dejan Milutinović David W. Casbeer Electrical and Computer Engineering Department University of California Santa Cruz CA USA Control Science Center of Excellence Air Force Research Laboratory Wright-Patterson AFB OH

ISBN: (纸本)9781538679012;9781538679265

Avoiding collisions with obstacles is of fundamental importance for the safe navigation of unmanned aerial vehicles (UAVs) and mobile robots. In this paper, we approach the avoidance problem by composing a scalable navigation strategy from multiple stochastic optimal controllers. We consider a scenario with a fixed speed Dubins vehicle, which is tasked to reach a waypoint while avoiding collisions with multiple moving obstacles. Obstacle moving directions are unknown, therefore, we use a random walk stochastic process model to anticipate that uncertainty in the design of navigation feedback control. The proposed navigation is based on a composition of minimum time stochastic optimal controllers. Each optimal controller is the solution to a minimum time problem to reach either the waypoint or a safe configuration with respect to an obstacle. The composition is based on the controller value functions and is scalable, i.e., it can deal with any number of obstacles. Our results are illustrated with a numerical simulation.

关键词： Navigation Optimal control Stochastic processes Collision avoidance Unmanned aerial vehicles Uncertainty Mobile robots

SSAM: A Haskell Parallel Programming STM Based Simple Actor Model

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Journal of Physics: Conference Series 2020年第1期1566卷

作者： Y Kim J Cheon T Hur S Byun G Woo Dep. of Electrical and Computer Engineering Pusan National University Dep. of Computer Science Kyungsung University Smart Control Center of LG Electronics

As computers with manycore architecture are being widely spread, parallel programming becomes a pending issue. While parallel programming has been a challenging issue, Haskell is known to be of the best available one. The immutability and declarative nature of Haskell suit well the need for parallelism. In our previous work, we implemented the SAM, a parallel programming model based on Haskell. In this paper, we propose the SSAM, an updated version of SAM, by solving the performance overhead of SAM socket. We discuss the architecture of SSAM and its major functions and show the 14% scalability upgrade in a performance test.

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Master equations and quantum trajectories for squeezed wave packets

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arXiv 2021年

作者： Gross, Jonathan A. Baragiola, Ben Stace, T.M. Combes, Joshua Center for Quantum Information and Control University of New Mexico AlbuquerqueNM87131-0001 United States Institut Quantique Université de Sherbrooke SherbrookeQCJ1K 2R1 Canada Centre for Quantum Computation & Communication Technology School of Science RMIT University MelbourneVIC3000 Australia ARC Centre for Engineered Quantum System Department of Physics University of Queensland BrisbaneQLD4072 Australia Department of Electrical Computer and Energy Engineering University of Colorado Boulder BoulderCO80309 United States

The interaction between matter and squeezed light has mostly been treated within the approximation that the field correlation time is small. Methods for treating squeezed light with more general correlations currently involve explicitly modeling the systems producing the light. We develop a general purpose input-output theory for a particular form of narrowband squeezed light-a squeezed wave-packet mode-that only cares about the statistics of the squeezed field and the shape of the wave packet. This formalism allows us to derive the input-output relations and the master equation. We also consider detecting the scattered field using photon counting and homodyne measurements which necessitates the derivation of the stochastic master equation. The non Markovian nature of the field manifests itself in the master equation as a coupled hierarchy of equations. We illustrate these with consequences for the decay and resonance fluorescence of two-level atoms in the presence of such fields. Copyright © 2021, The Authors. All rights reserved.

关键词： Wave packets