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arXiv 2023年

作者： Nocerino, Elisabetta Stuhr, Uwe Lorenzo, Irene San Mazza, Federico Mazzone, Daniel G. Hellsvik, Johan Hasegawa, Shunsuke Asai, Shinichiro Masuda, Takatsugu Minelli, Arianna Hossain, Zakir Thamizhavel, Arumugam Lefmann, Kim Sassa, Yasmine Månsson, Martin Itoh, S. Department of Applied Physics KTH Royal Institute of Technology StockholmSE-106 91 Sweden Laboratory for Neutron Scattering and Imaging Paul Scherrer Institute PSI VilligenCH-5232 Switzerland Nanoscience Center Niels Bohr Institute University of Copenhagen Nørre Allé 59 Copenhagen ODK-2100 Denmark Department of Applied Science and Technology Politecnico di Torino Corso Duca degli Abruzzi 24 Torino10129 Italy Institute of Solid State Physics Vienna University of Technology Wiedner Hauptstraße 8–10 Vienna1040 Austria PDC Center for High Performance Computing KTH Royal Institute of Technology StockholmSE-100 44 Sweden Nordita KTH Royal Institute of Technology Stockholm University Hannes Alfvéns väg 12 StockholmSE-106 91 Sweden Neutron Science Laboratory Institute for Solid State Physics The University of Tokyo Chiba Kashiwa277-8581 Japan Institute of Materials Structure Science High Energy Accelerator Research Organization Ibaraki305-0801 Japan Inorganic Chemistry Laboratory University of Oxford OxfordOX1 3QR United Kingdom Department of Physics Indian Institute of Technology Kanpur208016 India DCMPMS Tata Institute of Fundamental Research Mumbai400005 India Department of Physics Chalmers University of Technology GöteborgSE-412 96 Sweden

This paper reports the first experimental observation of phonons and their softening on single crystalline LaPt2Si2 via inelastic neutron scattering. From the temperature dependence of the phonon frequency in close proximity to the charge-density wave (CDW) q-vector, we obtain a CDW transition temperature of TCDW = 230 K and a critical exponent β = 0.28 ± 0.03. This value is suggestive of a non-conventional critical behavior for the CDW phase transition in LaPt2Si2, compatible with a scenario of CDW discommensuration (DC). The DC would be caused by the existence of two CDWs in this material, propagating separately in the non equivalent (Si1–Pt2-Si1) and (Pt1–Si2-Pt1) layers respectively, with transition temperatures TCDW−1 = 230 K and TCDW−2 = 110 K. A strong q-dependence of the electron-phonon coupling has been identified as the driving mechanism for the CDW transition at TCDW−1 = 230 K while a CDW with 3-dimensional character, and Fermi surface quasi-nesting as a driving mechanism, is suggested for the transition at TCDW−2 = 110 K. Our results clarify some aspects of the CDW transition in LaPt2Si2, which have been so far misinterpreted by both theoretical predictions and experimental observations, and give direct insight into its actual temperature dependence. © 2023, CC BY.

关键词： Charge density waves

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AdS3 Einstein Gravity and Boundary Description: Pedagogical Review

arXiv

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arXiv 2023年

作者： Ma, Chen-Te Department of Physics and Astronomy Iowa State University AmesIA50011 United States Asia Pacific Center for Theoretical Physics Pohang University of Science and Technology Gyeongsangbuk-do Pohang37673 Korea Republic of Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum Matter South China Normal University Guangdong Guangzhou510006 China School of Physics and Telecommunication Engineering South China Normal University Guangdong Guangzhou510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter Southern Nuclear Science Computing Center South China Normal University Guangzhou510006 China The Laboratory for Quantum Gravity and Strings Department of Mathematics and Applied Mathematics University of Cape Town Private Bag Rondebosch7700 South Africa

We review the various aspects of the 3D Einstein gravity theory with a negative cosmological constant and its boundary description. We also explore its connections to CFTs, modular symmetry, and holography. It is worth noting that this particular theory is topological in nature, which means that all the physical degrees of freedom are located on the boundary. Additionally, we can derive the boundary description on a torus, which takes the form of a 2D Schwarzian theory. This observation suggests that the relevant degrees of freedom for the theory can be described using this 2D theory. Because of the renormalizability of the 3D gravity theory, one can probe the quantum regime. This suggests that it is possible to investigate quantum phenomena. Unlike the conventional CFTs, when considering the AdS3 background, the boundary theory loses modular symmetry. This represents a departure from the usual behavior of CFT and is quite intriguing. The Weyl transformation induces anomaly in CFTs, and we indicate that applying this transformation to the 2D Schwarzian theory leads to similar results. Summing over all geometries with the asymptotic AdS3 boundary condition is equivalent to summing over a modular group. The partition function is one-loop exact and therefore an analytical expression from the summation. This theory holds potential applications in Quantum Information and is a recurring theme in the study of holography, where gravitational theories are connected with CFTs. Copyright © 2023, The Authors. All rights reserved.

关键词： Holography

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From High-Entropy Alloys to High-Entropy Ceramics: The Radiation-Resistant Highly Concentrated Refractory Carbide (CrNbTaTiW)C

SSRN

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SSRN 2023年

作者： Tunes, Matheus Araujo Fritze, Stefan Osinger, Barbara Willenshofer, Patrick Alvarado, Andrew M. Martinez, Enrique Menon, Ashok S. Ström, Petter Greaves, Graeme Lewin, Erik Jansson, Ulf Pogatscher, Stefan Saleh, Tarik A. Vishnyakov, Vladimir M. El-Atwani, Osman Materials Science and Technology Division Los Alamos National Laboratory Los AlamosNM87545 United States Department of Chemistry Angstrom Laboratory Uppsala University UppsalaSE-751 21 Sweden Department of Physics and Astronomy Applied Nuclear Physics Uppsala University UppsalaSE-751 21 Sweden Theoretical Division Los Alamos National Laboratory Los AlamosNM87545 United States Department of Materials Science and Engineering Clemson University ClemsonSC29623 United States Department of Mechanical Engineering Clemson University ClemsonSC29623 United States Chair of Non-Ferrous Metallurgy Montanuniversität Leoben8700 Austria School of Computing and Engineering University of Huddersfield HuddersfieldHD1 3DH United Kingdom

High-entropy materials represent the state-of-the-art on the alloy design strategy for future applications in extreme environments. Recent data indicates that high-entropy alloys (HEAs) exhibit outstanding radiation resistance in face of existing diluted alloy counterparts due to suppressed damage formation and evolution. An extension of the HEA concept is presented in this paper towards the synthesis and characterization of novel high-entropy ceramics as emergent materials for application in environments where energetic particle irradiation is a major concern. A novel carbide within the quinary refractory system CrNbTaTiW has been synthesized using magnetron-sputtering. The material exhibited nanocrystalline grains, singlephase crystal structure and C content around 50 at.%. Heavy-ion irradiation with in-situ Transmission Electron Microscopy was used to assess the irradiation response of the new highentropy carbide (HEC) at 573 K and a comparison with the HEA within the system is made. No displacement damage effects appear within the microstructures of both HEA and HEC up to a dose of 17 displacements-per-atom. Surprisingly, the HEC has not amorphized under the investigated conditions. Xe was implanted in both materials and bubbles nucleated, but smaller sizes compared with conventional nuclear materials shedding light they are potential candidates for use in nuclear energy. © 2023, The Authors. All rights reserved.

关键词： Entropy

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Learning the temporal evolution of multivariate densities via normalizing flows

arXiv

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arXiv 2021年

作者： Lu, Yubin Maulik, Romit Gao, Ting Dietrich, Felix Kevrekidis, Ioannis G. Duan, Jinqiao School of Mathematics and Statistics Center for Mathematical Sciences Huazhong University of Science and Technology Wuhan430074 China Argonne Leadership Computing Facility Argonne National Laboratory LemontIL60439 United States Department of Applied Mathematics College of Computing Illinois Institute of Technology ChicagoIL60616 United States Department of Informatics Technical University of Munich Boltzmannstr. 3 Garching b. Munich 85748 Germany Departments of Applied Mathematics and Statistics & Chemical and Biomolecular Engineering Johns Hopkins University BaltimoreMD21211 United States

In this work, we propose a method to learn multivariate probability distributions using sample path data from stochastic differential equations. Specifically, we consider temporally evolving probability distributions (e.g., those produced by integrating local or nonlocal Fokker-Planck equations). We analyze this evolution through machine learning assisted construction of a time-dependent mapping that takes a reference distribution (say, a Gaussian) to each and every instance of our evolving distribution. If the reference distribution is the initial condition of a Fokker-Planck equation, what we learn is the time-T map of the corresponding solution. Specifically, the learned map is a multivariate normalizing flow that deforms the support of the reference density to the support of each and every density snapshot in time. We demonstrate that this approach can approximate probability density function evolutions in time from observed sampled data for systems driven by both Brownian and Lévy noise. We present examples with two- and three-dimensional, uni- and multimodal distributions to validate the method. Copyright © 2021, The Authors. All rights reserved.

关键词： Gaussian noise (electronic)

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Optically Heralded Entanglement of Superconducting Systems in Quantum Networks

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Physical Review Letters 2021年第4期127卷 040503-040503页

作者： Stefan Krastanov Hamza Raniwala Jeffrey Holzgrafe Kurt Jacobs Marko Lončar Matthew J. Reagor Dirk R. Englund Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA John A. Paulson School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA U.S. Army Research Laboratory Computational and Information Sciences Directorate Adelphi Maryland 20783 USA Department of Physics University of Massachusetts at Boston Boston Massachusetts 02125 USA Rigetti Computing 775 Heinz Avenue Berkeley California 94710 USA Research Laboratory of Electronics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA

Networking superconducting quantum computers is a longstanding challenge in quantum science. The typical approach has been to cascade transducers: converting to optical frequencies at the transmitter and to microwave frequencies at the receiver. However, the small microwave-optical coupling and added noise have proven formidable obstacles. Instead, we propose optical networking via heralding end-to-end entanglement with one detected photon and teleportation. This new protocol can be implemented on standard transduction hardware while providing significant performance improvements over transduction. In contrast to cascaded direct transduction, our scheme absorbs the low optical-microwave coupling efficiency into the heralding step, thus breaking the rate-fidelity trade-off. Moreover, this technique unifies and simplifies entanglement generation between superconducting devices and other physical modalities in quantum networks.

关键词： Entanglement production Optical & microwave phenomena Quantum entanglement Quantum networks Superconducting qubits

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Deep learning-based similarity retrieval in clinical 3D gait analysis

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Gait & Posture 2021年 90卷 127-128页

作者： P. Krondorfer D. Slijepčević F. Unglaube A. Kranzl C. Breiteneder M. Zeppelzauer B. Horsak University of Applied Sciences Technikum Wien Institute of Life Science Engineering Vienna Austria St. Pölten University of Applied Sciences Institute of Creative∖Media/Technologies St. Pölten Austria Orthopaedic Hospital Vienna-Speising Laboratory of Gait and Movement Analysis Vienna Austria TU Wien Institute of Visual Computing and Human-Centered Technology Vienna Austria St. Pölten University of Applied Sciences Institute of Health Sciences St. Pölten Austria

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Deep learning-based damage mapping with InSAR coherence time series

arXiv

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arXiv 2021年

作者： Stephenson, Oliver L. Köhne, Tobias Zhan, Eric Cahill, Brent E. Yun, Sang-Ho Ross, Zachary E. Simons, Mark The Seismological Laboratory Division of Geological and Planetary Sciences California Institute of Technology PasadenaCA91125 United States The Department of Computing and Mathematical Sciences Division of Engineering and Applied Science California Institute of Technology PasadenaCA91125 United States REMY Biosciences 17802 Sky Park Circle Suite 100 IrvineCA92614 United States The Jet Propulsion Laboratory California Institute of Technology PasadenaCA91109 United States

Satellite remote sensing is playing an increasing role in the rapid mapping of damage after natural disasters. In particular, synthetic aperture radar (SAR) can image the Earth's surface and map damage in all weather conditions, day and night. However, current SAR damage mapping methods struggle to separate damage from other changes in the Earth's surface. In this study, we propose a novel approach to damage mapping, combining deep learning with the full time history of SAR observations of an impacted region in order to detect anomalous variations in the Earth's surface properties due to a natural disaster. We quantify Earth surface change using time series of Interferometric SAR coherence, then use a recurrent neural network (RNN) as a probabilistic anomaly detector on these coherence time series. The RNN is first trained on pre-event coherence time series, and then forecasts a probability distribution of the coherence between pre- and post-event SAR images. The difference between the forecast and observed co-event coherence provides a measure of the confidence in the identification of damage. The method allows the user to choose a damage detection threshold that is customized for each location, based on the local behavior of coherence through time before the event. We apply this method to calculate estimates of damage for three earthquakes using multi-year time series of Sentinel-1 SAR acquisitions. Our approach shows good agreement with observed damage and quantitative improvement compared to using preto co-event coherence loss as a damage proxy. Copyright © 2021, The Authors. All rights reserved.

关键词： Synthetic aperture radar

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Disorder-induced topological pumping on a superconducting quantum processor

arXiv

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arXiv 2024年

作者： Liu, Yu Zhang, Yu-Ran Shi, Yun-Hao Liu, Tao Lu, Congwei Wang, Yong-Yi Li, Hao Li, Tian-Ming Deng, Cheng-Lin Zhou, Si-Yun Liu, Tong Zhang, Jia-Chi Liang, Gui-Han Mei, Zheng-Yang Ma, Wei-Guo Liu, Hao-Tian Liu, Zheng-He Chen, Chi-Tong Huang, Kaixuan Song, Xiaohui Zhao, S.P. Tian, Ye Xiang, Zhongcheng Zheng, Dongning Nori, Franco Xu, Kai Fan, Heng Institute of Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100049 China School of Physics and Optoelectronics South China University of Technology Guangzhou510640 China Beijing Academy of Quantum Information Sciences Beijing100193 China Department of Physics Applied Optics Beijing Normal University Beijing100875 China Songshan Lake Materials Laboratory Guangdong Dongguan523808 China Hefei National Laboratory Hefei230088 China CAS Center for Excellence in Topological Quantum Computation UCAS Beijing100049 China Theoretical Quantum Physics Laboratory Cluster for Pioneering Research RIKEN Wako-shi Saitama351-0198 Japan Center for Quantum Computing RIKEN Saitama Wako-shi351-0198 Japan Physics Department University of Michigan Ann ArborMI48109-1040 United States

Thouless pumping, a dynamical version of the integer quantum Hall effect, represents the quantized charge pumped during an adiabatic cyclic evolution. Here we report experimental observations of nontrivial topological pumping that is induced by disorder even during a topologically trivial pumping trajectory. With a 41-qubit superconducting quantum processor, we develop a Floquet engineering technique to realize cycles of adiabatic pumping by simultaneously varying the on-site potentials and the hopping couplings. We demonstrate Thouless pumping in the presence of disorder and show its breakdown as the strength of disorder increases. Moreover, we observe two types of topological pumping that are induced by on-site potential disorder and hopping disorder, respectively. Especially, an intrinsic topological pump that is induced by quasi-periodic hopping disorder has never been experimentally realized before. Our highly controllable system provides a valuable quantum simulating platform for studying various aspects of topological physics in the presence of disorder. © 2024, CC BY.

关键词： Quantum Hall effect

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Loss tangent fluctuations due to two-level systems in superconducting microwave resonators

arXiv

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arXiv 2024年

作者： Vallières, André Russell, Megan E. You, Xinyuan Garcia-Wetten, David A. Goronzy, Dominic P. Walker, Mitchell J. Bedzyk, Michael J. Hersam, Mark C. Romanenko, Alexander Lu, Yao Grassellino, Anna Koch, Jens McRae, Corey Rae H. Graduate Program in Applied Physics Northwestern University EvanstonIL60208 United States Fermi National Accelerator Laboratory BataviaIL60510 United States Department of Physics and Astronomy Northwestern University EvanstonIL60208 United States Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Department of Chemistry Northwestern University EvanstonIL60208 United States Department of Electrical and Computer Engineering Northwestern University EvanstonIL60208 United States Center for Applied Physics and Superconducting Technologies Northwestern University EvanstonIL60208 United States Electrical Computing and Energy Engineering Department University of Colorado BoulderCO80309 United States Department of Physics University of Colorado BoulderCO80309 United States National Institute of Standards and Technology BoulderCO80305 United States

Superconducting microwave resonators are critical to quantum computing and sensing technologies. Additionally, they are common proxies for superconducting qubits when determining the effects of performance-limiting loss mechanisms such as from two-level systems (TLS). The extraction of these loss mechanisms is often performed by measuring the internal quality factor Qi as a function of power or temperature. In this work, we investigate large temporal fluctuations of Qi at low powers over periods of 12 to 16 hours (relative standard deviation σQi/Qi = 13%). These fluctuations are ubiquitous across multiple resonators, chips and cooldowns. We are able to attribute these fluctuations to variations in the TLS loss tangent due to two main indicators. First, measured fluctuations decrease as power and temperature increase. Second, for interleaved measurements, we observe correlations between low- and medium-power Qi fluctuations and an absence of correlations with high-power fluctuations. Agreement with the TLS loss tangent mean is obtained by performing measurements over a time span of a few hours. We hypothesize that, in addition to decoherence due to coupling to individual near-resonant TLS, superconducting qubits are affected by these observed TLS loss tangent fluctuations. © 2024, CC BY.

关键词： Qubits

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Generalized Quantum Subspace Expansion

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Physical Review Letters 2022年第2期129卷 020502-020502页

作者： Nobuyuki Yoshioka Hideaki Hakoshima Yuichiro Matsuzaki Yuuki Tokunaga Yasunari Suzuki Suguru Endo Department of Applied Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Theoretical Quantum Physics Laboratory RIKEN Cluster for Pioneering Research (CPR) Wako-shi Saitama 351-0198 Japan Research Center for Emerging Computing Technologies National Institute of Advanced Industrial Science and Technology (AIST) 1-1-1 Umezono Tsukuba Ibaraki 305-8568 Japan Center for Quantum Information and Quantum Biology Osaka University 1-2 Machikaneyama Toyonaka 560-0043 Japan NEC-AIST Quantum Technology Cooperative Research Laboratory National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Ibaraki 305-8568 Japan NTT Computer and Data Science Laboratories NTT Corporation Musashino 180-8585 Japan JST PRESTO 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan

One of the major challenges for erroneous quantum computers is undoubtedly the control over the effect of noise. Considering the rapid growth of available quantum resources that are not fully fault tolerant, it is crucial to develop practical hardware-friendly quantum error mitigation (QEM) techniques to suppress unwanted errors. Here, we propose a novel generalized quantum subspace expansion method which can handle stochastic, coherent, and algorithmic errors in quantum computers. By fully exploiting the substantially extended subspace, we can efficiently mitigate the noise present in the spectra of a given Hamiltonian, without relying on any information of noise. The performance of our method is discussed under two highly practical setups: the quantum subspaces are mainly spanned by powers of the noisy state ρm and a set of error-boosted states, respectively. We numerically demonstrate in both situations that we can suppress errors by orders of magnitude, and show that our protocol inherits the advantages of previous error-agnostic QEM techniques as well as overcoming their drawbacks.

关键词： Quantum algorithms Quantum computation Quantum error correction Quantum information processing Variational approach

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