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Magnetless Circulators with Harmonic Rejection Based on N-Way Cyclic-Symmetric Time-Varying Networks

Physical Review Applied 2019年第2期12卷 024046-024046页

作者： Ahmed Kord Harish Krishnaswamy Andrea Alù Department of Electrical and Computer Engineering The University of Texas at Austin Austin Texas 78712 USA Department of Electrical Engineering Columbia University New York New York 10027 USA Photonics Initiative Advanced Science Research Center City University of New York New York New York 10031 USA Physics Program Graduate Center City University of New York New York New York 10026 USA Department of Electrical Engineering City College of New York New York New York 10031 USA

Magnetfree circulators are crucial devices to enable full-duplex communications with the goal of enhancing the spectral efficiency of wireless radios compared to currently deployed half-duplex systems. Nevertheless, implementations proposed to date at radio- and millimeter-wave frequencies have been based on spatiotemporally modulating a discrete number of nonlinear elements, such as varactors or switched capacitors, which, despite achieving strong nonreciprocity, suffer from spurious emission in adjacent channels and limited power handling. These problems jeopardize the practical use of these components in many applications, including wireless communications and quantum computing, and make them less attractive compared to harmonicfree magnetic devices. We address these problems by introducing N-way circulators, which consist of N spatiotemporally modulated angular-momentum (STM AM) biased units connected either in series or in parallel and modulated through a rotating phase pattern. We show that these circuits, for a sufficiently large N, effectively impart an overall linear and continuous angular-momentum bias, which significantly reduces spurious emission and increases the overall power handling. This, in turn, strengthens the argument of magnetless circulators compared to their magnetic counterparts, and opens exciting venues to address the realistic needs of practical systems.

关键词： Electromagnetism Metamaterials Photonics Quantum information with hybrid systems Devices T-symmetry

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Object retrieval in past video using bag-of-words model 6

Object retrieval in past video using bag-of-words model

引用

6th International Conference on Control, Automation and Information sciences, ICCAIS 2017

作者： Nguyen-Hoang, Manh-Tien Le, Tu-Khiem Ninh, Van-Tu Che, Quoc-Huu Nguyen, Vinh-Tiep Tran, Minh-Triet Advanced Program in Computer Science University of Science Viet Nam Multimedia Communications Laboratory University of Information Technology Viet Nam Faculty of Information Technology University of Science Viet Nam

ISBN: (纸本)9781538631140

Together with the technology advancement, computer Vision plays an important role in enhancing smart computing systems to help people overcome obstacles in their daily lives. One of the common troublesome problems is human memorization ability, especially memorizing things such as personal items. It is annoying for people to waste their time finding lost items manually by recall or notes. This motivates the authors to propose a solution that can help a user find an item that he or she already saw but vaguely remembers where and when it appeared in the past. The user simply provides our system a single image of that item, then the system retrieves a rank list of visual scenes that may contain the item from video recorded implicitly during user's daily activities. Our method is based on Bag-of-Words model, one of the most famous methods in image retrieval. We first conduct experiments to find the appropriate parameters and configurations of Bag-of-Words system for visual instance search. Then we perform experiments with 110 visual queries of 30 common objects in real video with 2837 shots recorded during daily activities of volunteers. Experimental results show that for all 30/30 categories of objects, our system can help users find their objects of interest just by looking into the top 10 video shots retrieved from recorded video with the balance accuracy from 50 to 80%. This demonstrates the potential use of our method to help people remind of their items in an easy and comfortable way. © 2017 IEEE.

关键词： Image retrieval

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Low-rank solution methods for stochastic eigenvalue problems

arXiv

引用

arXiv 2018年

作者： Elman, Howard C. Su, Tengfei Department of Computer Science Institute for Advanced Computer Studies University of Maryland College ParkMD20742 United States Applied Mathematics & Statistics Scientific Computation Program University of Maryland College ParkMD20742 United States

We study efficient solution methods for stochastic eigenvalue problems arising from discretization of self-adjoint partial differential equations with random data. With the stochastic Galerkin approach, the solutions are represented as generalized polynomial chaos expansions. A low-rank variant of the inverse subspace iteration algorithm is presented for computing one or several minimal eigenvalues and corresponding eigenvectors of parameter-dependent matrices. In the algorithm, the iterates are approximated by low-rank matrices, which leads to significant cost savings. The algorithm is tested on two benchmark problems, a stochastic diffusion problem with some poorly separated eigenvalues, and an operator derived from a discrete stochastic Stokes problem whose minimal eigenvalue is related to the inf-sup stability constant. Numerical experiments show that the low-rank algorithm produces accurate solutions compared to the Monte Carlo method, and it uses much less computational time than the original algorithm without low-rank approximation. Copyright © 2018, The Authors. All rights reserved.

关键词： Eigenvalues and eigenfunctions

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DeePMD-kit v2: A software package for Deep Potential models

arXiv

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arXiv 2023年

作者： Zeng, Jinzhe Zhang, Duo Lu, Denghui Mo, Pinghui Li, Zeyu Chen, Yixiao Rynik, Marián Huang, Li'ang Li, Ziyao Shi, Shaochen Wang, Yingze Ye, Haotian Tuo, Ping Yang, Jiabin Ding, Ye Li, Yifan Tisi, Davide Zeng, Qiyu Bao, Han Xia, Yu Huang, Jiameng Muraoka, Koki Wang, Yibo Chang, Junhan Yuan, Fengbo Bore, Sigbjørn Løland Cai, Chun Lin, Yinnian Wang, Bo Xu, Jiayan Zhu, Jia-Xin Luo, Chenxing Zhang, Yuzhi Goodall, Rhys E.A. Liang, Wenshuo Singh, Anurag Kumar Yao, Sikai Zhang, Jingchao Wentzcovitch, Renata Han, Jiequn Liu, Jie Jia, Weile York, Darrin M. Weinan, E. Car, Roberto Zhang, Linfeng Wang, Han Laboratory for Biomolecular Simulation Research Institute for Quantitative Biomedicine Department of Chemistry and Chemical Biology Rutgers University PiscatawayNJ08854 United States AI for Science Institute Beijing100080 China DP Technology Beijing100080 China Academy for Advanced Interdisciplinary Studies Peking University Beijing100871 China HEDPS CAPT College of Engineering Peking University Beijing100871 China College of Electrical and Information Engineering Hunan University Changsha China Yuanpei College Peking University Beijing100871 China Program in Applied and Computational Mathematics Princeton University PrincetonNJ08540 United States Department of Experimental Physics Comenius University Mlynská Dolina F2 Bratislava842 48 Slovakia Center for Quantum Information Institute for Interdisciplinary Information Sciences Tsinghua University Beijing100084 China Center for Data Science Peking University Beijing100871 China ByteDance Research Zhonghang Plaza No. 43 North 3rd Ring West Road Haidian District Beijing China College of Chemistry and Molecular Engineering Peking University Beijing100871 China Baidu Inc. Beijing China Key Laboratory of Structural Biology of Zhejiang Province School of Life Sciences Westlake University Zhejiang Hangzhou China Westlake AI Therapeutics Lab Westlake Laboratory of Life Sciences and Biomedicine Zhejiang Hangzhou China Department of Chemistry Princeton University PrincetonNJ08544 United States SISSA Scuola Internazionale Superiore di Studi Avanzati Trieste34136 Italy Laboratory of Computational Science and Modeling Institute of Materials École Polytechnique Fédérale de Lausanne Lausanne1015 Switzerland Department of Physics National University of Defense Technology Hunan Changsha410073 China State Key Lab of Processors Institute of Computing Technology Chinese Academy of Sciences Beijing China University of Chinese Academy of Sciences Beijing China School of Electronics Engineerin

DeePMD-kit is a powerful open-source software package that facilitates molecular dynamics simulations using machine learning potentials (MLP) known as Deep Potential (DP) models. This package, which was released in 2017, has been widely used in the fields of physics, chemistry, biology, and material science for studying atomistic systems. The current version of DeePMD-kit offers numerous advanced features such as DeepPot-SE, attention-based and hybrid descriptors, the ability to fit tensile properties, type embedding, model deviation, Deep Potential - Range Correction (DPRc), Deep Potential Long Range (DPLR), GPU support for customized operators, model compression, non-von Neumann molecular dynamics (NVNMD), and improved usability, including documentation, compiled binary packages, graphical user interfaces (GUI), and application programming interfaces (API). This article presents an overview of the current major version of the DeePMD-kit package, highlighting its features and technical details. Additionally, the article benchmarks the accuracy and efficiency of different models and discusses ongoing developments. © 2023, CC BY-NC-ND.

关键词： Molecular dynamics

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Event-based moving object detection and tracking

arXiv

引用

arXiv 2018年

作者： Mitrokhin, Anton Fermüller, Cornelia Parameshwara, Chethan Aloimonos, Yiannis Department of Computer Science University of Maryland College ParkMD20740 United States Institute for Advanced Computer Studies University of Maryland College ParkMD20740 United States Neuroscience and Cognitive Science Program University of Maryland College ParkMD20740 United States

Event-based vision sensors, such as the Dynamic Vision Sensor (DVS), are ideally suited for real-time motion analysis. The unique properties encompassed in the readings of such sensors provide high temporal resolution, superior sensitivity to light and low latency. These properties provide the grounds to estimate motion efficiently and reliably in the most sophisticated scenarios, but these advantages come at a price - modern event-based vision sensors have extremely low resolution, produce a lot of noise and require the development of novel algorithms to handle the asynchronous event stream. This paper presents a new, efficient approach to object tracking with asynchronous cameras. We present a novel event stream representation which enables us to utilize information about the dynamic (temporal) component of the event stream. The 3D geometry of the event stream is approximated with a parametric model to motion-compensate for the camera (without feature tracking or explicit optical flow computation), and then moving objects that don't conform to the model are detected in an iterative process. We demonstrate our framework on the task of independent motion detection and tracking, where we use the temporal model inconsistencies to locate differently moving objects in challenging situations of very fast motion. Copyright © 2018, The Authors. All rights reserved.

关键词： Object detection

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Optomechanically Induced Birefringence and Faraday Effect

arXiv

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arXiv 2019年

作者： Duggan, Robert del Pino, Javier Verhagen, Ewold Alù, Andrea Department of Electrical and Computer Engineering University of Texas at Austin AustinTX78712 United States Center for Nanophotonics AMOLF Science Park 104 Amsterdam1098 XG Netherlands Photonics Initiative Advanced Science Research Center City University of New York NY10031 United States Physics Program Graduate Center City University of New York NY10016 United States Department of Electrical Engineering City College of The City University of New York NY10031 United States

We demonstrate an optomechanical platform where optical mode conversion mediated by mechanical motion enables arbitrary tailoring of polarization states of propagating light fields. Optomechanical interactions are realized in a Fabry-Perót resonator, which naturally supports two polarization-degenerate states while an optical control field induces rotational symmetry breaking. Applying such principles, the entire Poincaré sphere is spanned by just optical control of the driving field, realizing reciprocal and non-reciprocal optomechanically-induced birefringence for linearly polarized and circularly polarized control driving. A straightforward extension of this setup also enables all-optical tunable isolation and circulation. Our findings open new avenues to exploit optomechanics for arbitrary manipulation of light polarization. Copyright © 2019, The Authors. All rights reserved.

关键词： Birefringence

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A Basis Set of Elementary Operations Captures Recombination of Neocortical Cell Assemblies during Basal Conditions and Learning

SSRN

引用

SSRN 2019年

作者： Aschauer, Dominik F. Eppler, Jens-Bastian Ewig, Luke Chambers, Anna Pokorny, Christoph Kaschube, Matthias Rumpel, Simon Institute of Physiology Focus Program Translational Neurosciences University Medical Center Johannes Gutenberg University-Mainz Mainz Germany Frankfurt Institute of Advanced Studies Goethe University Frankfurt Frankfurt /M. Germany Institute of Basic Medical Sciences Faculty of Medicine University of Oslo Oslo Norway Institute of Theoretical Computer Science Graz University of Technology Graz Austria Department of Basic Neurosciences University of Geneva Geneva Switzerland

Cell assemblies — subgroups within neuronal networks — are believed to serve as functional entities underlying cognitive capabilities such as categorical perception or memory formation and storage. However, little is known about their long-term dynamics. Using chronic in vivo calcium imaging in the mouse auditory cortex, we find that cell assemblies undergo continuous recombination, even under behaviorally stable conditions. We identify a basis set of elementary operations capturing the dynamics of cell assemblies, which involve plasticity of both the stimulus tuning of particular assemblies as well as the cellular composition of an assembly. Auditory fear conditioning introduces biases in the frequency of specific cell assembly operations that lead to increased association of representations and improved sound encoding. Thus, decomposing cell assembly dynamics during basal conditions into a basis set of elementary operations provides a general framework to explain learning-induced changes in global population activity. © 2019, The Authors. All rights reserved.

关键词： Neurons

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The 2022 report of the Lancet Countdown on health and climate change: health at the mercy of fossil fuels (vol 400, pg 1619, 2022)

引用

LANCET 2022年第10365期400卷 1766-1766页

作者： Romanello, M. Di Napoli, C. Drummond, P. Institute for Global Health University College London London UK School of Agriculture Policy and Development University of Reading Reading UK Institute for Sustainable Resources University College London London UK Department of Global Health Centre for Health and the Global Environment University of Washington Seattle WA USA UCL Energy Institute University College London London UK Department of Health Sciences University of York York UK Department of Meteorology University of Reading Reading UK Institute for Risk and Disaster Reduction University College London London UK School of Earth and Environment University of Leeds Leeds UK Centre on Climate Change and Planetary Health London School of Hygiene & Tropical Medicine London UK School of Population Health University of Melbourne Melbourne VIC Australia Department of Earth System Science Tsinghua University Beijing China Mercator Research Institute on Global Commons and Climate Change Berlin Germany Department of Environment Climate Change and Health World Health Organization Geneva Switzerland Institute of Environmental Sciences University of Geneva Geneva Switzerland Cardiovascular Epidemiology Unit Department of Public Health & Primary Care University of Cambridge Cambridge UK School of Government University of Birmingham Birmingham UK Economic Analysis of Climate Impacts and Policy Division Centro Euro-Mediterraneo sui Cambiamenti Climatici Venice Italy Institute for Environmental Design and Engineering University College London London UK Natural Resources Institute University of Greenwich London UK Department of Environmental Health Sciences and Yale Center on Climate Change and Health Yale University New Haven CT USA Department of Civil and Environmental Engineering Northeastern University Boston MA USA Department of Fish and Wildlife Conservation Virginia Polytechnic Institute and State University Blacksburg VA USA Department of Geography University College London London UK NU

With advancements in the science of detection and attribution studies, the influence of climate change over many events has now been quantified. Because of the rapidly increasing temperatures, vulnerable populations (adults older than 65 years, and children younger than one year of age) were exposed to 3·7 billion more heatwave days in 2021 than annually in 1986–2005 (indicator 1.1.2), and heat-related deaths increased by 68% between 2000–04 and 2017–21 (indicator 1.1.5), a death toll that was significantly exacerbated by the confluence of the COVID-19 pandemic. Despite the local cooling and overall health benefits of urban greenspaces, only 277 (27%) of 1038 global urban centres were at least moderately green in 2021 (indicator 2.2.3), and the number of households with air conditioning increased by 66% from 2000 to 2020, a maladaptive response that worsens the energy crisis and further increases urban heat, air pollution, and greenhouse gas emissions. [...]millions of people do not have access to the energy needed to keep their homes at healthy temperatures, preserve food and medication, and meet the seventh Sustainable Development Goal (to ensure access to affordable, reliable, sustainable, and modern energy for all). Aggravating this situation even further, governments continue to incentivise fossil fuel production and consumption: 69 (80%) of 86 countries reviewed had net-negative carbon prices (ie, provided a net subsidy to fossil fuels) for a net total of US$400 billion

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Agents, subsystems, and the conservation of information

arXiv

引用

arXiv 2018年

作者： Chiribella, Giulio Department of Computer Science University of Oxford Parks Road Oxford United Kingdom Canadian Institute for Advanced Research CIFAR Program in Quantum Information Science Department of Computer Science University of Hong Kong Pokfulam Road Hong Kong HKU Shenzhen Institute of Research and Innovation Kejizhong 2nd Road Shenzhen China

Dividing the world into subsystems is an important component of the scientific method. The choice of subsystems, however, is not defined a priori. Typically, it is dictated by experimental capabilities, which may be different for different agents. Here we propose a way to define subsystems in general physical theories, including theories beyond quantum and classical mechanics. Our construction associates every agent A with a subsystem SA, equipped with its set of states and its set of transformations. In quantum theory, this construction accommodates the notion of subsystems as factors of a tensor product Hilbert space, as well as the notion of subsystems associated to a subalgebra of operators. Classical systems can be interpreted as subsystems of quantum systems in different ways, by applying our construction to agents who have access to different sets of operations, including multiphase covariant channels and certain sets of free operations arising in the resource theory of quantum coherence. After illustrating the basic definitions, we restrict our attention to closed systems, that is, systems where all physical transformations act invertibly and where all states can be generated from a fixed initial state. For closed systems, we propose a dynamical definition of pure states, and show that all the states of all subsystems admit a canonical purification. This result extends the purification principle to a broader setting, in which coherent superpositions can be interpreted as purifications of incoherent mixtures. Copyright © 2018, The Authors. All rights reserved.

关键词： Purification

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Quantum communication in a superposition of causal orders

arXiv

引用

arXiv 2018年

作者： Salek, Sina Ebler, Daniel Chiribella, Giulio Department of Computer Science University of Oxford Parks Road United Kingdom United Kingdom Department of Computer Science University of Hong Kong Pokfulam Road Hong Kong Canadian Institute for Advanced Research CIFAR Program in Quantum Information Science TorontoONM5G 1Z8 Canada

Quantum mechanics allows for situations where the relative order between two processes is entangled with a quantum degree of freedom. Here we show that such entanglement can enhance the ability to transmit quantum information over noisy communication channels. We consider two completely dephasing channels, which in normal conditions are unable to transmit any quantum information. We show that, when the two channels are traversed in an indefinite order, a quantum bit sent through them has a 25% probability to reach the receiver without any error. For partially dephasing channels, a similar advantage takes place deterministically: The amount of quantum information that can travel through two channels in a superposition of orders can be larger than the amount of quantum information that can travel through each channel individually. Copyright © 2018, The Authors. All rights reserved.

关键词： Quantum optics

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