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Variational approach to the dynamics of dissipative quantum impurity models

Physical Review B 2025年第15期111卷 155113-155113页

作者： Yi-Fan Qu Martino Stefanini Tao Shi Tilman Esslinger Sarang Gopalakrishnan Jamir Marino Eugene Demler Institute for Theoretical Physics ETH Zurich 8093 Zurich Switzerland Institut für Physik Johannes Gutenberg-Universität Mainz D-55099 Mainz Germany CAS Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100190 China CAS Center for Excellence in Topological Quantum Computation & School of Physical Sciences University of Chinese Academy of Sciences Beijing 100049 China Institute for Quantum Electronics & Quantum Center ETH Zurich 8093 Zurich Switzerland Department of Electrical and Computer Engineering Princeton University Princeton New Jersey 08540 USA

Recent experiments with quantum simulators using ultracold atoms and superconducting qubits have demonstrated the potential of controlled dissipation as a versatile tool for realizing correlated many-body states. However, determining the dynamics of dissipative quantum many-body systems remains a significant analytical and numerical challenge. In this paper, we focus on a dissipative impurity problem as a testbed for new methodological developments. We introduce an efficient nonperturbative framework that combines the superposition of Gaussian states variational ansatz with the quantum trajectory approach to simulate open systems featuring a dissipative impurity. Applying this method to a spinful impurity subject to two-body losses and embedded in a bath of noninteracting fermions, we explore the full crossover from weak to strong dissipation regimes. The nonperturbative nature of the SGS ansatz allows us to thoroughly examine this crossover, providing comprehensive insights into the behavior of the system. In the strong dissipation regime, our approach reproduces the finding that localized two-body losses can induce the Kondo effect [Stefanini et al., arXiv:2406.03527], characterized by a slowdown of spin relaxation and an enhancement of charge conductance. Furthermore, we reveal an exotic negative conductance phenomenon at zero potential bias—a counterintuitive single-body effect resulting from intermediate dissipation and finite bandwidth. Finally, we investigate the formation of ferromagnetic domains and propose an extension to realize a higher-spin Kondo model using localized dissipation.

关键词： Variational techniques

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Constrained Optimization with Decision-Dependent Distributions

arXiv

引用

arXiv 2023年

作者： Wang, Zifan Liu, Changxin Parisini, Thomas Zavlanos, Michael M. Johansson, Karl H. Division of Decision and Control Systems School of Electrical Engineering and Computer Science KTH Royal Institute of Technology Sweden Digital Futures StockholmSE-10044 Sweden The Department of Electrical and Electronic Engineering Imperial College London LondonSW7 2AZ United Kingdom The Department of Engineering and Architecture University of Trieste Trieste34127 Italy The KIOS Research and Innovation Center of Excellence University of Cyprus NicosiaCY-1678 Cyprus The Department of Mechanical Engineering and Materials Science Duke University DurhamNC United States

In this paper we deal with stochastic optimization problems where the data distributions change in response to the decision variables. Traditionally, the study of optimization problems with decision-dependent distributions has assumed either the absence of constraints or fixed constraints. This work considers a more general setting where the constraints can also dynamically adjust in response to changes in the decision variables. Specifically, we consider linear constraints and analyze the effect of decision-dependent distributions in both the objective function and constraints. Firstly, we establish a sufficient condition for the existence of a constrained equilibrium point, at which the distributions remain invariant under retraining. Morevoer, we propose and analyze two algorithms: repeated constrained optimization and repeated dual ascent. For each algorithm, we provide sufficient conditions for convergence to the constrained equilibrium point. Furthermore, we explore the relationship between the equilibrium point and the optimal point for the constrained decision-dependent optimization problem. Notably, our results encompass previous findings as special cases when the constraints remain fixed. To show the effectiveness of our theoretical analysis, we provide numerical experiments on both a market problem and a dynamic pricing problem for parking based on real-world data. Copyright © 2023, The Authors. All rights reserved.

关键词： Constrained optimization

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Fault-tolerant quantum computation using large spin cat-codes

arXiv

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arXiv 2024年

作者： Omanakuttan, Sivaprasad Buchemmavari, Vikas Gross, Jonathan A. Deutsch, Ivan H. Marvian, Milad Center for Quantum Information and Control University of New Mexico AlbuquerqueNM United States Department of Physics and Astronomy University of New Mexico AlbuquerqueNM United States Google Quantum AI VeniceCA90291 United States Department of Electrical and Computer Engineering University of New Mexico AlbuquerqueNM87131 United States

We construct a fault-tolerant quantum error-correcting protocol based on a qubit encoded in a large spin qudit using a spin-cat code, analogous to the continuous variable cat encoding. With this, we can correct the dominant error sources, namely processes that can be expressed as error operators that are linear or quadratic in the components of angular momentum. Such codes tailored to dominant error sources can exhibit superior thresholds and lower resource overheads when compared to those designed for unstructured noise models. A key component is the CNOT gate that preserves the rank of spherical tensor operators. Categorizing the dominant errors as phase and amplitude errors, we demonstrate how phase errors, analogous to phase-flip errors for qubits, can be effectively corrected. Furthermore, we propose a measurement-free error correction scheme to address amplitude errors without relying on syndrome measurements. Through an in-depth analysis of logical CNOT gate errors, we establish that the fault-tolerant threshold for error correction in the spin-cat encoding surpasses that of standard qubit-based encodings. We consider a specific implementation based on neutral-atom quantum computing, with qudits encoded in the nuclear spin of 87Sr, and show how to generate the universal gate set, including the rank-preserving CNOT gate, using quantum control and the Rydberg blockade. These findings pave the way for encoding a qubit in a large spin with the potential to achieve fault tolerance, high threshold, and reduced resource overhead in quantum information processing. © 2024, CC0.

关键词： Qubits

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A novel deep learning method for textual sentiment analysis

arXiv

引用

arXiv 2021年

作者： Sadr, Hossein Solimandarabi, Mozhdeh Nazari Pedram, Mir Mohsen Teshnehlab, Mohammad Department of Computer Engineering Rasht Branch Islamic Azad University Rasht Iran Department of Electrical and Computer Engineering Faculty of Engineering Kharazmi University Tehran Iran Industrial Control Center of Excellence Faculty of Electrical and Computer Engineering K. N. Toosi University Tehran Iran

Sentiment analysis is known as one of the most crucial tasks in the field of natural language processing and Convolutional Neural Network (CNN) is one of those prominent models that is commonly used for this aim. Although convolutional neural networks have obtained remarkable results in recent years, they are still confronted with some limitations. Firstly, they consider that all words in a sentence have equal contributions in the sentence meaning representation and are not able to extract informative words. Secondly, they require a large number of training data to obtain considerable results while they have many parameters that must be accurately adjusted. To this end, a convolutional neural network integrated with a hierarchical attention layer is proposed which is able to extract informative words and assign them higher weight. Moreover, the effect of transfer learning that transfers knowledge learned in the source domain to the target domain with the aim of improving the performance is also explored. Based on the empirical results, the proposed model not only has higher classification accuracy and can extract informative words but also applying incremental transfer learning can significantly enhance the classification performance. © 2021, CC BY.

关键词： Sentiment analysis

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AdaptiveClick: Clicks-aware Transformer with Adaptive Focal Loss for Interactive Image Segmentation

arXiv

引用

arXiv 2023年

作者： Lin, Jiacheng Chen, Jiajun Yang, Kailun Roitberg, Alina Li, Siyu Li, Zhiyong Li, Shutao The College of Computer Science and Electronic Engineering Hunan University Changsha410082 China The School of Robotics The National Engineering Research Center of Robot Visual Perception and Control Technology Hunan University Changsha410082 China The Institute for Artificial Intelligence The University of Stuttgart Stuttgart70569 Germany The College of Electrical and Information Engineering The Key Laboratory of Visual Perception and Artificial Intelligence of Hunan Province Hunan University Changsha410082 China

Interactive Image Segmentation (IIS) has emerged as a promising technique for decreasing annotation time. Substantial progress has been made in pre- and post-processing for IIS, but the critical issue of interaction ambiguity, notably hindering segmentation quality, has been under-researched. To address this, we introduce ADAPTIVECLICK – a click-aware transformer incorporating an adaptive focal loss that tackles annotation inconsistencies with tools for mask- and pixel-level ambiguity resolution. To the best of our knowledge, AdaptiveClick is the first transformer-based, mask-adaptive segmentation framework for IIS. The key ingredient of our method is the Click-Aware Mask-adaptive transformer Decoder (CAMD), which enhances the interaction between click and image features. Additionally, AdaptiveClick enables pixel-adaptive differentiation of hard and easy samples in the decision space, independent of their varying distributions. This is primarily achieved by optimizing a generalized Adaptive Focal Loss (AFL) with a theoretical guarantee, where two adaptive coefficients control the ratio of gradient values for hard and easy pixels. Our analysis reveals that the commonly used Focal and BCE losses can be considered special cases of the proposed AFL. With a plain ViT backbone, extensive experimental results on nine datasets demonstrate the superiority of AdaptiveClick compared to state-of-the-art methods. The source code is publicly available at https://***/lab206/AdaptiveClick. Copyright © 2023, The Authors. All rights reserved.

关键词： Pixels

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Overview of Ancillary Services in the Nigerian Power Sector 2

Overview of Ancillary Services in the Nigerian Power Sector

引用

2nd International Conference on Multidisciplinary engineering and Applied Science, ICMEAS 2023

作者： Saka, Bemdoo Hussein, Suleiman U. Ishola, Biliaminu A. Mohammed, Yekini S. Hembe, Nanen D. Mustapha, Umar M. Thomas, Sadiq Nile University of Nigeria Dept. of Electrical/Electronics Eng. Abuja Nigeria Centre for Satellite Tech. Development Nat. Space Research and Dev. Agency Abuja Nigeria National Control Center Transmission Company of Nigeria Osogbo Abuja Nigeria Federal Polytechnic Nasarawa Dept. of Electrical/Electronics Eng. Nasarawa Nigeria Nasarawa State University Department of Geography Nasarawa Nigeria Advanced UAV Laboratory Nat. Space Research and Dev. Agency Abuja Nigeria Nile University of Nigeria Dept. of Computer Engineering Abuja Nigeria

ISBN: (纸本)9798350358834

An overview of the ancillary services in the Nigerian power sector is provided in this work. These services are essential in the power system because they are additional services required by the grid during critical times to enable the power grid to operate in a stable, safe, and reliable manner. The ancillary services provided as stipulated in the Grid Code are black start, frequency control, operating reserves, and voltage control. The System Operator procures the relevant ancillary service depending on the requirement of the grid at a particular time. The paper further presents some ways of improving the viability of ancillary services for the energy grid of Nigeria. These include making incentives more attractive for suppliers of ancillary services, utilizing more hydroelectric power plants for generation and load balancing, integrating distributed generation to provide support to the reactive power, and making necessary investments in the grid. © 2023 IEEE.

关键词： Hydroelectric power plants

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Detailed Investigation of Bio-Foam Characteristics of Piggery Wastewater Reveals Novel Foaming Mechanisms

SSRN

引用

SSRN 2023年

作者： Cheng, Peijin Zhang, Jianming Zhang, Kaiji Liu, Yang Xu, Xiangyang Zhu, Liang Institute of Environment Pollution Control and Treatment Department of Environmental Engineering Zhejiang University Hangzhou310058 China Zhejiang Province Key Laboratory for Water Pollution Control and Environmental Safety Hangzhou310058 China Zhejiang Provincial Engineering Laboratory of Water Pollution Control Hangzhou310058 China Hangzhou Xiaokai Technology Co. Ltd. Hangzhou310000 China Innovation Center of Yangtze River Delta Zhejiang University Jiashan314100 China Department of Electrical and Computer Engineering Samueli School of Engineering University of California Los AngelesCA United States Department of Environmental Engineering Zhejiang University No. 866 Yuhangtang Road Hangzhou310058 China

Biological foam has seriously troubled the wastewater treatment process and brings major challenges to effluent quality, process efficiency, and operation safety. This study systematically analyzed bio-foam characteristics from three piggery wastewater treatment stations to reveal potential foaming mechanisms. The low surface tension for piggery wastewater led to strong foaming capacity, and high viscosity and Zeta potential contributed to foam stability. The long-chain fatty acids (LCFAs) in wastewater were proved to be the key components responsible for foaming: the decrease of surface tension caused by LCFAs directly induced strong foaming ability (physicochemical path);moreover, LCFAs favored the enrichment of non-filamentous foam-related microbes like Hydrogenophaga and Pseudomonas to secrete extracellular polymeric substances, increasing the viscosity and Zeta potential to maintain foam stability (biological paths). Based on the revealed foaming mechanism dominated by LCFAS, this study provided novel insight and valuable guidance for the efficient and safe treatment of piggery wastewater. © 2023, The Authors. All rights reserved.

关键词： Surface tension

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Coverage Probability Analysis of RIS-Assisted High-Speed Train Communications

Coverage Probability Analysis of RIS-Assisted High-Speed Tra...

引用

IEEE Conference on Wireless Communications and Networking

作者： Changzhu Liu Ruisi He Yong Niu Bo Ai Zhu Han Meilin Gao Zhangdui Zhong State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing China Research Center of Networks and Communications Peng Cheng Laboratory Shenzhen China Department of Electrical and Computer Engineering University of Houston Houston USA Beijing National Research Center for Information Science and Technology Tsinghua University China

Reconfigurable intelligent surface (RIS) has received increasing attention due to its capability of extending cell coverage by reflecting signals toward receivers. This paper considers a RIS-assisted high-speed train (HST) communication system to improve coverage probability. We derive the closed-form expression of coverage probability. Moreover, we analyze impacts of some key system parameters, including transmission power, signal-to-noise ratio threshold, and horizontal distance between base station and RIS. Simulation results verify the efficiency of RIS-assisted HST communications in terms of coverage probability.

关键词： Wireless communication Base stations Closed-form solutions Simulation Receivers Downlink Signal to noise ratio

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Decentralized temperature and storage volume control in multi-producer district heating

arXiv

引用

arXiv 2022年

作者： Martinez, Juan Eduardo Machado Ferguson, Joel Cucuzzella, Michele Scherpen, Jacquelien M.A. The Jan C. Willems Center for Systems and Control ENTEG Faculty of Science and Engineering University of Groningen Nijenborgh 4 Groningen9747 AG Netherlands The School of Engineering The University of Newcastle Australia The Department of Electrical Computer and Biomedical Engineering University of Pavia via Ferrata 5 Pavia27100 Italy

Modern district heating technologies have a great potential to make the energy sector more flexible and sustainable due to their capabilities to use energy sources of varied nature and to efficiently store energy for subsequent use. Central control tasks within these systems for the efficient and safe distribution of heat refer to the stabilization of overall system temperatures and the regulation of storage units state of charge. These are challenging goals when the networked and nonlinear nature of district heating system models is taken into consideration. In this letter, for district heating systems with multiple, distributed heat producers, we propose a decentralized control scheme to provably meet said tasks stably. Copyright © 2022, The Authors. All rights reserved.

关键词： District heating

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Effective Two-Stage Double Auction for Dynamic Resource Trading in Edge Networks via Overbooking

arXiv

引用

arXiv 2025年

作者： Wu, Sicheng Liwang, Minghui Wang, Deqing Wang, Xianbin Wu, Chao Tang, Junyi Li, Li Jiao, Zhenzhen The School of Informatics Xiamen University Fujian China The Department of Control Science and Engineering The National Key Laboratory of Autonomous Intelligent Unmanned Systems Tongji University Shanghai China Frontiers Science Center for Intelligent Autonomous Systems Ministry of Education Tongji University Shanghai China The Department of Electrical and Computer Engineering Western University ON Canada The School of Public Affairs Zhejiang University Hangzhou310027 China School of Information Science and Engineering Lanzhou University Lanzhou China The iF-Labs Beijing Teleinfo Technology Co. Ltd. CAICT China

To facilitate responsive and cost-effective computing resource scheduling and service delivery over edge-assisted mobile networks, this paper investigates a novel two-stage double auction methodology via utilizing an interesting idea of resource overbooking to overcome dynamic and uncertain nature from edge servers (sellers) and demand from mobile devices (as buyers). The proposed auction integrates multiple essential factors such as social welfare maximization and decision-making latency (e.g., the time for determining winning seller-buyer pairs) reduction, by introducing a stagewise strategy: an overbooking-driven pre-double auction (OPDAuction) for determining long-term cooperations between sellers and buyers before practical resource transactions as Stage I, and a real-time backup double auction (RBDAuction) for handling residual resource demands during actual transactions. In particular, by applying a proper overbooking rate, OPDAuction helps with facilitating trading contracts between appropriate sellers and buyers as guidance for future transactions, by allowing the booked resources to exceed supply. Then, since pre-auctions may cause risks, our RBDAuction adjusts to real-time market changes, further enhancing the overall social welfare. More importantly, we offer an interesting view to show that our proposed two-stage auction can support significant design properties such as truthfulness, individual rationality, and budget balance. Through extensive experiments, we demonstrate good performance in social welfare, time efficiency, and computational scalability, outstripping conventional methods in dynamic edge computing settings. Copyright © 2025, The Authors. All rights reserved.

关键词： Budget control

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