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arXiv 2021年

作者： Coleman, Matthew S.B. Rafikov, Roman R. Philippov, Alexander A. Institute for Advanced Study Einstein Drive PrincetonNJ08540 United States Department of Astrophysical Sciences Princeton University 4 Ivy Lane PrincetonNJ08540 United States Centre for Mathematical Sciences Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road CambridgeCB3 0WA United Kingdom Center for Computational Astrophysics Flatiron Institute 162 Fifth Avenue New YorkNY10010 United States

Disk accretion onto weakly magnetized objects possessing a material surface must proceed via the so-called boundary layer (BL)-a region at the inner edge of the disk, in which the velocity of accreting material abruptly decreases from its Keplerian value. Supersonic shear arising in the BL is known to be conducive to excitation of acoustic waves that propagate into both the accretor and the disk, enabling angular momentum and mass transport across the BL. We carry out a numerical exploration of different wave modes that operate near the BL, focusing on their morphological characteristics in the innermost parts of accretion disk. Using a large suite of simulations covering a broad range of Mach numbers (of the supersonic shear flow in the BL), we provide accurate characterization of the different types of modes, verifying their properties against analytical results, when available. We discover new types of modes, in particular, global spiral density waves launched by vortices forming in the disk near the BL as a result of the Rossby wave instability;this instability is triggered by the vortensity production in that region caused by the nonlinear damping of acoustic waves. Azimuthal wavenumbers of the dominant modes that we observe appear to increase monotonically with the Mach number of the runs, but a particular mix of modes found in a simulation is mildly stochastic. Our results provide a basis for better understanding of the angular momentum and mass transport across the BL as well as the emission variability in accreting objects. © 2021, CC BY.

关键词： Angular momentum

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Asymmetric Loop Spectra and Unbroken Phase Protection due to Nonlinearities in PT-Symmetric Periodic Potentials

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Physical Review Letters 2021年第3期127卷 034101-034101页

作者： Yongping Zhang Zhu Chen Biao Wu Thomas Busch Vladimir V. Konotop International Center of Quantum Artificial Intelligence for Science and Technology (QuArtist) and Department of Physics Shanghai University Shanghai 200444 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Wilczek Quantum Center School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China Quantum Systems Unit Okinawa Institute of Science and Technology Graduate University Okinawa 904-0495 Japan Centro de Física Teórica e Computacional and Departamento de Física Faculdade de Ciências Universidade de Lisboa Campo Grande 2 Edifício C8 Lisboa 1749-016 Portugal

We demonstrate that the interplay between a nonlinearity and PT symmetry in a periodic potential results in peculiar features of nonlinear periodic solutions. These include thresholdless symmetry breaking and asymmetric (multi-)loop structures of the nonlinear Bloch spectrum, persistence of unbroken PT symmetry even after the gap is closed, nonmonotonic dependence of the PT phase transition on the defocusing nonlinearity, and enhanced stability of the nonlinear states corresponding to the loop structures. The asymmetry and the loop structure of the spectrum are explained within the framework of a two-mode approximation and an effective potential theory and are validated numerically.

关键词： Nonlinear beam dynamics Nonlinear optics Nonlinear waves PT-symmetry

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A deep learning-based ODE solver for chemical kinetics

arXiv

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arXiv 2020年

作者： Zhang, Tianhan Zhang, Yaoyu Weinan, E. Ju, Yiguang Department of Mechanical and Aerospace Engineering Princeton University PrincetonNJ08544 United States School of Mathematical Sciences Institute of Natural Sciences MOE-LSC Qing Yuan Research Institute Shanghai Jiao Tong University Shanghai200240 China Department of Mathematics Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

Developing efficient and accurate algorithms for chemistry integration is a challenging task due to its strong stiffness and high dimensionality. The current work presents a deep learning-based numerical method called DeepCombustion0.0 to solve stiff ordinary differential equation systems. The homogeneous autoignition of DME/air mixture, including 54 species, is adopted as an example to illustrate the validity and accuracy of the algorithm. The training and testing datasets cover a wide range of temperature, pressure, and mixture conditions between 750 – 1200 K, 30 – 50 atm, and equivalence ratio = 0.7 – 1.5. Both the first-stage low-temperature ignition (LTI) and the second-stage high-temperature ignition (HTI) are considered. The methodology highlights the importance of the adaptive data sampling techniques, power transform preprocessing, and binary deep neural network (DNN) design. By using the adaptive random samplings and appropriate power transforms, smooth submanifolds in the state vector phase space are observed, on which two three-layer DNNs can be appropriately trained. The neural networks are end-to-end, which predict temporal gradients of the state vectors directly. The results show that temporal evolutions predicted by DNN agree well with traditional numerical methods in all state vector dimensions, including temperature, pressure, and species concentrations. Besides, the ignition delay time differences are within 1%. At the same time, the CPU time is reduced by more than 20 times and 200 times compared with the HMTS and VODE method, respectively. The current work demonstrates the enormous potential of applying the deep learning algorithm in chemical kinetics and combustion modeling. © 2020, CC BY.

关键词： Numerical methods

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Correction to: A dual layer security scheme for medical images using Hessenberg and singular value decompositions

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Multimedia Tools and Applications 2022年第10期81卷 14023-14023页

作者： Elmoasry, Ahmed Khan, Lal Said Khan, Majid Hussain, Iqtadar Department of Mathematics College of Science Al-Zulfi Majmaah University Al-Zulfi Saudi Arabia Department of Avionics Engineering Institute of Space Technology Islamabad Pakistan Department of Applied Mathematics and Statistics Institute of Space Technology Islamabad Pakistan Mathematics Program Department of Mathematics Statistics and Physics College of Arts and Sciences Qatar University Doha Qatar Statistical Consulting Unit College of Arts and Science Qatar University Doha Qatar

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Direct Monitoring of Li2S2Evolution and Its Influence on the Reversible Capacities of Lithium-Sulfur Batteries

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Angewandte Chemie 2023年第11期135卷

作者： Dr. Yufeng Luo Dr. Zhenhan Fang Dr. Shaorong Duan Hengcai Wu Dr. Haitao Liu Dr. Yuxing Zhao Dr. Ke Wang Prof. Qunqing Li Prof. Shoushan Fan Prof. Zijian Zheng Prof. Wenhui Duan Prof. Yuegang Zhang Prof. Jiaping Wang Tsinghua-Foxconn Nanotechnology Research Center Tsinghua University Beijing 100084 China Laboratory for Advanced Interfacial Materials and Devices School of Fashion and Textiles The Hong Kong Polytechnic University Hong Kong SAR 99077 China Department of Physics Tsinghua University Beijing 100084 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China School of Materials Science and Technology China University of Geosciences Beijing 100083 China Frontier Science Center for Quantum Information Tsinghua University Beijing 100084 China State Key Laboratory of Low-Dimensional Quantum Physics Tsinghua University Beijing 100084 China

The polysulfide (PS) dissolution and low conductivity of lithium sulfides (Li 2 S) are generally considered the main reasons for limiting the reversible capacity of the lithium-sulfur (Li-S) system. However, as the inevitable intermediate between PSs and Li 2 S, lithium disulfide (Li 2 S 2 ) evolutions are always overlooked. Herein, Li 2 S 2 evolutions are monitored from the operando measurements on the pouch cell level. Results indicate that Li 2 S 2 undergoes slow electrochemical reduction and chemical disproportionation simultaneously during the discharging process, leading to further PS dissolution and Li 2 S generation without capacity contribution. Compared with the fully oxidized Li 2 S, Li 2 S 2 still residues at the end of the charging state. Therefore, instead of the considered Li 2 S and PSs, slow electrochemical conversions and side chemical reactions of Li 2 S 2 are the determining factors in limiting the sulfur utilization, corresponding to the poor reversible capacity of Li-S batteries.

关键词： Lithium Disulfides Chemical Reactions Conductive Interlayer Lithium Sulfur Battery Operando Measurement

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Traceable random numbers from a nonlocal quantum advantage

arXiv

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arXiv 2024年

作者： Kavuri, Gautam A. Palfree, Jasper Reddy, Dileep V. Zhang, Yanbao Bienfang, Joshua C. Mazurek, Michael D. Alhejji, Mohammad A. Siddiqui, Aliza U. Cavanagh, Joseph M. Dalal, Aagam Abellán, Carlos Amaya, Waldimar Mitchell, Morgan W. Stange, Katherine E. Beale, Paul D. Brandão, Luís T.A.N. Booth, Harold Peralta, René Nam, Sae Woo Mirin, Richard P. Stevens, Martin J. Knill, Emanuel Shalm, Lynden K. Department of Physics University of Colorado BoulderCO80309 United States The National Institute of Standards and Technology BoulderCO80305 United States Quantum Information Science Section Computational Sciences and Engineering Division Oak Ridge National Laboratory Oak RidgeTN37831 United States Joint Quantum Institute National Institute of Standards and Technology University of Maryland 100 Bureau Drive GaithersburgMD20899 United States Center for Quantum Information and Control University of New Mexico AlbuquerqueNM87131 United States Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Physical Measurement Laboratory National Institute of Standards and Technology GaithersburgMD20899 United States Quside Technologies S.L. Castelldefels Barcelona Spain ICFO-Institut de Ciencies Fotoniques The Barcelona Institute of Science and Technology Castelldefels Barcelona08860 Spain ICREA - Institució Catalana de Recerca i Estudis Avançats Barcelona08010 Spain Department of Mathematics University of Colorado BoulderCO80309 United States GaithersburgMD20899 United States Information Technology Laboratory National Institute of Standards and Technology GaithersburgMD20899 United States Physical Measurement Laboratory National Institute of Standards and Technology BoulderCO80305 United States Center for Theory of Quantum Matter University of Colorado BoulderCO80305 United States Applied and Computational Mathematics Division National Institute of Standards and Technology BoulderCO80305 United States Quantum Engineering Initiative Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States

The unpredictability of random numbers is fundamental to both digital security [1, 2] and applications that fairly distribute resources [3, 4]. However, existing random number generators have limitations—the generation processes cannot be fully traced, audited, and certified to be unpredictable. The algorithmic steps used in pseudorandom number generators [5] are auditable, but they cannot guarantee that their outputs were a priori unpredictable given knowledge of the initial seed. Device-independent quantum random number generators [6–9] can ensure that the source of randomness was unknown beforehand, but the steps used to extract the randomness are vulnerable to tampering. Here, for the first time, we demonstrate a fully traceable random number generation protocol based on device-independent techniques. Our protocol extracts randomness from unpredictable non-local quantum correlations, and uses distributed intertwined hash chains to cryptographically trace and verify the extraction process. This protocol is at the heart of a public traceable and certifiable quantum randomness beacon that we have launched [10]. Over the first 40 days of operation, we completed the protocol 7434 out of 7454 attempts—a success rate of 99.7%. Each time the protocol succeeded, the beacon emitted a pulse of 512 bits of traceable randomness. The bits are certified to be uniform with error times actual success probability bounded by 2−64. The generation of certifiable and traceable randomness represents one of the first public services that operates with an entanglement-derived advantage over comparable classical approaches. Copyright © 2024, The Authors. All rights reserved.

关键词： Random number generation

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Decoding electron tunnelling delay time by embracing wave-particle duality

arXiv

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arXiv 2021年

作者： Wang, Chuncheng Li, Xiaokai Liu, Xiwang Li, Jie Zhou, Shengpeng Yang, Yizhang Song, Xiaohong Chen, Jing Yang, Weifeng Ding, Dajun Institute of Atomic and Molecular Physics Advanced Light Field and Modern Medical Treatment Science and Technology Innovation Center of Jilin Province Jilin University Changchun130012 China Research Center for Advanced Optics and Photoelectronics Department of Physics College of Science Shantou University Guangdong515063 China Institute of Mathematics Shantou University Shantou Guangdong515063 China MOE Key Laboratory of Intelligent Manufacturing Technology Shantou University Shantou Guangdong515063 China Institute of Applied Physics and Computational Mathematics P.O. Box 8009 Beijing100088 China Laboratory for Physical Chemistry ETH Zürich Vladimir-Prelog-Weg 2 Zürich8093 Switzerland

Tunnelling lies at the heart of quantum mechanics and is a fundamental process in attosecond science, molecular biology, and quantum devices. Whether tunnelling takes time and how a microscopic particle transits through a barrier have been debated since the early days of quantum mechanics 1-9. The time required for an electron to tunnel through an atomic potential barrier has been measured with attosecond angular streaking (attoclock), and a recent work on the hydrogen atom claimed that electron tunnelling is instantaneous 10. However, the time required for Rb atoms to tunnel through an optical potential barrier has been measured to be on the order of milliseconds with a recent Larmor clock measurement 11. The essence of electron and atom tunnelling is identical, but the reason for the contradictory conclusions remains unknown. Here, we demonstrate that the sub-barrier potential interaction is the root of the nonzero tunnelling delay time. We reveal that the wave-particle duality of a tunnelling electron must be fully taken into account when decoding the tunnelling delay time from the attoclock measurements. Based on energy-resolved attoclock measurements, we show that the tunnelling delay time of an electron ranges from 24 to 58 attoseconds, and the counterintuitive result that an electron with a lower energy may spend less time in the barrier is consistent with the velocity-dependent tunnelling time of atoms in Larmor clock measurements 11. Our results unify the tunnelling time of microscopic particles by highlighting the classically forbidden sub-barrier potential interactions of matter waves. © 2021, CC BY-NC-ND.

关键词： Electrons

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Shut and re-open: The role of schools in the spread of COVID-19 in Europe

arXiv

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arXiv 2020年

作者： Stage, Helena B. Shingleton, Joseph Ghosh, Sanmitra Scarabel, Francesca Pellis, Lorenzo Finnie, Thomas Department of Mathematics The University of Manchester United Kingdom Joint Universities Pandemic and Epidemiological Research Emergency Response Department Public Health England United Kingdom MRC Biostatistics Unit University of Cambridge Cambridge United Kingdom Laboratory of Industrial and Applied Mathematics Department of Mathematics and Statistics York University TorontoON Canada CDLab - Computational Dynamics Laboratory Department of Mathematics Computer Science and Physics University of Udine Italy The Alan Turing Institute London United Kingdom

We investigate the effect of school closure and subsequent reopening on the transmission of COVID-19, by considering Denmark, Norway, Sweden, and German states as case studies. By comparing the growth rates in daily hospitalisations or confirmed cases under different interventions, we provide evidence that school closures contribute to a reduction in the growth rate approximately 7 days after implementation. Limited school attendance, such as older students sitting exams or the partial return of younger year groups, does not appear to significantly affect community transmission. In countries where community transmission is generally low, such as Denmark or Norway, a large-scale reopening of schools while controlling or suppressing the epidemic appears feasible. However, school reopening can contribute to statistically significant increases in the growth rate in countries like Germany, where community transmission is relatively high. In all regions, a combination of low classroom occupancy and robust test-and-trace measures were in place. Our findings underscore the need for a cautious evaluation of reopening strategies. Copyright © 2020, The Authors. All rights reserved.

关键词： Transmissions

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Exploring Modified Gravity: Constraints on the μ and Σ Parametrization with WMAP, ACT, and SPT

arXiv

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arXiv 2023年

作者： Andrade, Uendert Capistrano, Abraão J.S. Di Valentino, Eleonora Nunes, Rafael C. Leinweber Center for Theoretical Physics University of Michigan 450 Church Street Ann ArborMI48109-1040 United States Department of Physics College of Literature Science and the Arts University of Michigan 450 Church Street Ann ArborMI48109-1040 United States Observatório Nacional RJ Rio de Janeiro20921-400 Brazil Universidade Federal do Paraná PR Palotina85950-000 Brazil Applied physics graduation program UNILA PR Foz do Iguaçu85867-670 Brazil School of Mathematics and Statistics University of Sheffield United Kingdom Instituto de Física Universidade Federal do Rio Grande do Sul Porto Alegre RS 91501-970 Brazil Divisão de Astrofísica Instituto Nacional de Pesquisas Espaciais Avenida dos Astronautas 1758 SP São José dos Campos12227-010 Brazil

The cosmic acceleration problem remains one of the most significant challenges in cosmology. One of the proposed solutions to this problem is the modification of gravity on large scales. In this paper, we explore the well-known μ-Σ parametrization scenarios and confront them with observational data, including the cosmic microwave background (CMB) radiation from the Wilkinson Microwave Anisotropy Probe (WMAP), Atacama Cosmology Telescope (ACT), and South Pole Telescope (SPT), as well as large-scale structure data from the Sloan Digital Sky Survey (SDSS: BAO+RSD) and Pantheon Supernovae (SN) catalog. We employ a Bayesian framework to constrain the model parameters and discuss the implications of our results on the viability of modified gravity theories. Our analysis reveals the strengths and limitations of the μ-Σ parametrization and provides valuable insights into the nature of gravity on cosmological scales. From the joint analysis of the ACT + WMAP + SDSS + SN, we find μ0 − 1 = 0.02 ± 0.19 and Σ0 − 1 = 0.021 ± 0.068 at 68% CL. In light of the SPT + WMAP + SDSS + SN, we find μ0 − 1 = 0.07 ± 0.18 and Σ0 − 1 = −0.009+−0007811 at 68% CL. In all the analyses carried out, we do not find any deviations from the theory of general relativity. Our results represent an observational update on the well-known μ-Σ parameterization in view of current CMB data, independent and competitive with the constraints obtained with the Planck data. Copyright © 2023, The Authors. All rights reserved.

关键词： Telescopes

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Open Hardware Solutions in Quantum Technology

arXiv

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arXiv 2023年

作者： Shammah, Nathan Roy, Anurag Saha Almudever, Carmen G. Bourdeauducq, Sébastien Butko, Anastasiia Cancelo, Gustavo Clark, Susan M. Heinsoo, Johannes Henriet, Loïc Huang, Gang Jurczak, Christophe Kotilahti, Janne Landra, Alessandro LaRose, Ryan Mari, Andrea Nowrouzi, Kasra Ockeloen-Korppi, Caspar Prawiroatmodjo, Guen Siddiqi, Irfan Zeng, William J. Unitary Fund San FranciscoCA94104 United States Qruise GmbH Saarbruecken66113 Germany Technical University of Valencia Spain M-Labs Limited North Point Hong Kong Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Fermi National Accelerator Laboratory BataviaIL60510 United States Sandia National Laboratories AlbuquerqueNM87123 United States IQM Quantum Computers Espoo02150 Finland PASQAL 7 rue Leonard de Vinci Massy91300 France Accelerator Technology and Applied Physics Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Quantonation Paris75010 France Center for Quantum Computing Science and Engineering Michigan State University East LansingMI48824 United States School of Science and Technology Università di Camerino Camerino62032 Italy Microsoft Quantum RedmondWA98052 United States Quantum Nanoelectronics Laboratory Department of Physics University of California at Berkeley BerkeleyCA94720 United States

Quantum technologies such as communications, computing, and sensing offer vast opportunities for advanced research and development. While an open-source ethos currently exists within some quantum technologies, especially in quantum computer programming, we argue that there are additional advantages in developing open quantum hardware (OQH). Open quantum hardware encompasses open-source software for the control of quantum devices in labs, blueprints and open-source toolkits for chip design and other hardware components, as well as openly-accessible testbeds and facilities that allow cloud-access to a wider scientific community. We provide an overview of current projects in the OQH ecosystem, identify gaps, and make recommendations on how to close them today. More open quantum hardware would accelerate technology transfer to and growth of the quantum industry and increase accessibility in science. © 2023, CC BY.

关键词： Technology transfer

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