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Universal methods for variational inequalities: deterministic and stochastic cases

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arXiv 2024年

作者： Klimza, Anton Gasnikov, Alexander Stonyakin, Fedor Alkousa, Mohammad Moscow Institute of Physics and Technology Department of Applied Mathematics and Computer Science Institutsky lane 9 Dolgoprudny141701 Russia Innopolis University Universitetskaya Str. Innopolis420500 Russia Institute for Information Transmission Problems RAS Bolshoy Karetny per. 19 build.1 Moscow127051 Russia V. I. Vernadsky Crimean Federal University 4 Academician Vernadsky Avenue Simferopol295007 Russia

In this paper, we propose universal proximal mirror methods to solve the variational inequality problem with Hölder-continuous operators in both deterministic and stochastic settings. The proposed methods automatically adapt not only to the oracle’s noise (in the stochastic setting of the problem) but also to the Hölder continuity of the operator without having prior knowledge of either the problem class or the nature of the operator information. We analyzed the proposed algorithms in both deterministic and stochastic settings and obtained estimates for the required number of iterations to achieve a given quality of a solution to the variational inequality. We showed that, without knowing the Hölder exponent and Hölder constant of the operators, the proposed algorithms have the least possible in the worst-case sense complexity for the considered class of variational inequalities. We also compared the resulting stochastic algorithm with other popular optimizers for the task of image classification. © 2024, CC BY.

关键词： Mirrors

Ansatz-free Hamiltonian learning with Heisenberg-limited scaling

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arXiv 2025年

作者： Hu, Hong-Ye Ma, Muzhou Gong, Weiyuan Ye, Qi Tong, Yu Flammia, Steven T. Yelin, Susanne F. Department of Physics Harvard University CambridgeMA02138 United States Department of Electronic Engineering Tsinghua University Beijing China School of Engineering and Applied Sciences Harvard University AllstonMA02134 United States Center for Quantum Information IIIS Tsinghua University Beijing China Department of Mathematics Duke University DurhamNC27708 United States Department of Electrical and Computer Engineering Duke University DurhamNC27708 United States Duke Quantum Center Duke University DurhamNC27701 United States Department of Computer Science Virginia Tech AlexandriaVA22314 United States Phasecraft Inc. WashingtonDC United States

Learning the unknown interactions that govern a quantum system is crucial for quantum information processing, device benchmarking, and quantum sensing. The problem, known as Hamiltonian learning, is well understood under the assumption that interactions are local, but this assumption may not hold for arbitrary Hamiltonians. Previous methods all require high-order inverse polynomial dependency with precision, unable to surpass the standard quantum limit and reach the gold standard Heisenberg-limited scaling. Whether Heisenberg-limited Hamiltonian learning is possible without prior assumptions about the interaction structures, a challenge we term ansatz-free Hamiltonian learning, remains an open question. In this work, we present a quantum algorithm to learn arbitrary sparse Hamiltonians without any structure constraints using only black-box queries of the system’s real-time evolution and minimal digital controls to attain Heisenberg-limited scaling in estimation error. Our method is also resilient to state-preparation-and-measurement errors, enhancing its practical feasibility. Moreover, we establish a fundamental trade-off between total evolution time and quantum control on learning arbitrary interactions, revealing the intrinsic interplay between controllability and total evolution time complexity for any learning algorithm. These results pave the way for further exploration into Heisenberg-limited Hamiltonian learning in complex quantum systems under minimal assumptions, potentially enabling new benchmarking and verification protocols. © 2025, CC BY.

关键词： Hamiltonians

Endotaxial Stabilization of 2D Charge Density Waves with Long-range Order

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arXiv 2023年

作者： Sung, Suk Hyun Agarwal, Nishkarsh Baggari, Ismail El Goh, Yin Min Kezer, Patrick Schnitzer, Noah Liu, Yu Lu, Wenjian Sun, Yuping Kourkoutis, Lena F. Heron, John T. Sun, Kai Hovden, Robert Department of Materials Science and Engineering University of Michigan Ann ArborMI48109 United States Rowland Institute Harvard University CambridgeMA02142 United States John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States Department of Electrical and Computer Engineering University of Michigan Ann ArborMI48109 United States Department of Materials Science and Engineering Cornell University IthacaNY14853 United States Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei230031 China High Magnetic Field Laboratory Chinese Academy of Sciences Hefei230031 China Collaborative Innovation Centre of Advanced Microstructures Nanjing University Nanjing210093 China School of Applied and Engineering Physics Cornell University IthacaNY14853 United States Kavli Institute Cornell for Nanoscale Science IthacaNY14853 United States Applied Physics Program University of Michigan Ann ArborMI48109 United States Department of Physics University of Michigan Ann ArborMI48109 United States

Charge density waves are emergent quantum states that spontaneously reduce crystal symmetry, drive metal-insulator transitions, and precede superconductivity. In low-dimensions, distinct quantum states arise, however, thermal fluctuations and external disorder destroy long-range order. Here we stabilize ordered two-dimensional (2D) charge density waves through endotaxial synthesis of confined monolayers of 1T-TaS2. Specifically, an ordered incommensurate charge density wave (oIC-CDW) is realized in 2D with dramatically enhanced amplitude and resistivity. By enhancing CDW order, the hexatic nature of charge density waves becomes observable. Upon heating via in-situ TEM, the CDW continuously melts in a reversible hexatic process wherein topological defects form in the charge density wave. From these results, new regimes of the CDW phase diagram for 1T-TaS2 are derived and consistent with the predicted emergence of vestigial quantum order. © 2023, CC BY.

关键词： Charge density waves

All-optical measurement-device-free feedforward enabling ultra-fast quantum informationprocessing

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arXiv 2024年

作者： Yamashima, Taichi Kashiwazaki, Takahiro Suzuki, Takumi Nehra, Rajveer Nakamura, Tomohiro Inoue, Asuka Umeki, Takeshi Takase, Kan Asavanant, Warit Endo, Mamoru Furusawa, Akira Department of Applied Physics School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan NTT Device Technology Labs NTT Corporation 3-1 Morinosato Wakamiya Atsugi Kanagawa243-0198 Japan Department of Electrical and Computer Engineering University of Massachusetts Amherst AmherstMA01003 United States Department of Physics University of Massachusetts Amherst AmherstMA01003 United States College of Information and Computer Science University of Massachusetts Amherst AmherstMA01003 United States Optical Quantum Computing Research Team RIKEN Center for Quantum Computing 2-1 Hirosawa Wako Saitama351-0198 Japan

Utilizing feedforward to perform adaptive quantum operations on one entangled state according to the measurement result of the other state enables measurement-based quantum information processing (QIP). Until now, the bandwidth of feedforward in optical QIP has been limited to around 100 MHz by measurement with electronics. A potential alternative is the utilization of an optical parametric amplifier (OPA). This optical device eliminates the need for electronic measuring devices and enables all-optical broadband feedforward. In this paper, we demonstrate a variable squeezing gate with an operation bandwidth of 1.3 THz by all-optical measurement-device-free feedforward. We utilize a periodically poled lithium niobate waveguide as a broadband OPA and perform continuous phase locking in our optical system. Experimental results demonstrate that our all-optical QIP operates at a THz clock frequency, representing a major step toward the realization of an ultra-fast quantum computer. © 2024, CC BY.

关键词： Parametric amplifiers

Angle-resolved photoemission spectroscopy with an in situ tunable magnetic field

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arXiv 2023年

作者： Huang, Jianwei Yue, Ziqin Baydin, Andrey Zhu, Hanyu Nojiri, Hiroyuki Kono, Junichiro He, Yu Yi, Ming Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Smalley–Curl Institute Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States Institute for Materials Research Tohoku University Katahira 2-1-1 Sendai980-8577 Japan Department of Applied Physics Yale University New HavenCT06511 United States

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for probing the momentum-resolved single-particle spectral function of materials. Historically, in situ magnetic fields have been carefully avoided as they are detrimental to the control of photoelectron trajectory during the photoelectron detection process. However, magnetic field is an important experimental knob for both probing and tuning symmetry-breaking phases and electronic topology in quantum materials. In this paper, we introduce an easily implementable method for realizing an in situ tunable magnetic field at the sample position in an ARPES experiment and analyze magnetic field induced artifacts in ARPES data. Specifically, we identified and quantified three distinct extrinsic effects of a magnetic field: Constant energy contour rotation, emission angle contraction, and momentum broadening. We examined these effects in three prototypical quantum materials, i.e., a topological insulator (Bi2Se3), an iron-based superconductor (LiFeAs), and a cuprate superconductor (Pb-Bi2Sr2CuO6+x), and demonstrate the feasibility of ARPES measurements in the presence of a controllable magnetic field. Our studies lay the foundation for the future development of the technique and interpretation of ARPES measurements of field-tunable quantum phases. Copyright © 2023, The Authors. All rights reserved.

关键词： Photoelectrons

Comparative studies of the sensitivities of sparse and full geometries of Total-Body PET scanners built from crystals and plastic scintillators

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arXiv 2023年

作者： Dadgar, Meysam Parzych, Szymon Baran, Jakub Chug, Neha Curceanu, Catalina Czerwiński, Eryk Dulski, Kamil Elyan, Kavya Gajos, Aleksander Hiesmayr, Beatrix C. Kaplon, Lukasz Klimaszewski, Konrad Konieczka, Pawel Korcyl, Grzegorz Kozik, Tomasz Krzemień, Wojciech Kumar, Deepak Niedźwiecki, Szymon Panek, Domonik del Rio, Eleną Perez Raczyński, Lech Sharma, Sushil Shivani Shopa, Roman Y. Skurzok, Magdalena Stępień, Ewa L. Ardebili, Faranak Tayefi Ardebili, Keyvan Tayefi Vandenberghe, Stefaan Wiślicki, Wojciech Moskal, Pawel Faculty of Physics Astronomy and Applied Computer Science Poland Department of Experimental Particle Physics and Applications Jagiellonian University Krakow Poland Total-Body Jagiellonian-PET Laboratory Jagiellonian University Krakow Poland Theranostics Center Jagiellonian University Krakow Poland INFN Laboratori Nazionali di Frascati Frascati Italy Faculty of Physics University of Vienna Vienna Austria Department of Complex Systems National Centre for Nuclear Research Otwock-Swierk Poland High Energy Physics Division National Centre for Nuclear Research Otwock-Swierk Poland Department of Electronics and Information Systems MEDISIP Ghent University-IBiTech Gent Belgium

Background: Alongside the benefits of Total-Body imaging modalities, such as higher sensitivity, single-bed position, low dose imaging, etc., their final construction cost prevents worldwide utilization. The main aim of this study is to present a simulation-based comparison of the sensitivities of existing and currently developed tomographs to introduce a cost-efficient solution for constructing a Total-Body PET scanner based on plastic scintillators. Methods: For the case of this study, eight tomographs based on the uEXPLORER configuration with different scintillator materials (BGO, LYSO), axial field-of-view (97.4 cm and 194.8 cm), and detector configuration (full and sparse) were simulated. In addition, 8 J-PET scanners with different configurations, such as various axial field-of-view (200 cm and 250 cm), the different cross-sections of plastic scintillator, and the multiple numbers of the plastic scintillator layers (2, 3, and 4), based on J-PET technology have been simulated by GATE software. Furthermore, Biograph Vision has been simulated to compare the results with standard PET scans. Two types of simulations have been performed. The first one with a centrally located source with a diameter of 1mm and a length of 250 cm, and the second one with the same source inside a water-filled cylindrical phantom with a diameter of 20 cm and a length of 183 cm. Results: With regards to sensitivity, among all the proposed scanners, the ones constructed with BGO crystals give the best performance (∼ 350 cps/kBq at the center). The utilization of sparse geometry or LYSO crystals significantly lowers the achievable sensitivity of such systems. The J-PET design gives a similar sensitivity to the sparse LYSO crystal-based detectors while having full detector coverage over the body. Moreover, it provides uniform sensitivity over the body with additional gain on its sides and provides the possibility for high-quality brain imaging. Conclusion: Taking into account not only the s

关键词： Ionization

Non-equilibrium critical scaling and universality in a quantum simulator

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arXiv 2023年

作者： De, A. Cook, P. Collins, K. Morong, W. Paz, D. Titum, P. Pagano, G. Gorshkov, A.V. Maghrebi, M. Monroe, C. Joint Quantum Institute Joint Center for Quantum Information and Computer Science NIST University of Maryland College ParkMD20742 United States Department of Physics and Astronomy Michigan State University East LansingMI48824 United States Facility for Rare Isotope Beams East LansingMI48824 United States Johns Hopkins University Applied Physics Laboratory LaurelMD20723 United States Department of Physics and Astronomy Rice University HoustonTX United States Department of Electrical and Computer Engineering Department of Physics Duke Quantum Center Duke University DurhamNC27708 United States IonQ Inc. College ParkMD20742 United States

Universality and scaling laws are hallmarks of equilibrium phase transitions and critical phenomena1–3. However, extending these concepts to non-equilibrium systems is an outstanding challenge. Despite recent progress in the study of dynamical phases4,5, the universality classes and scaling laws for non-equilibrium phenomena are far less understood than those in equilibrium6. In this work, using a trapped-ion quantum simulator with single-ion resolution, we investigate the non-equilibrium nature of critical fluctuations following a quantum quench to the critical point. We probe the scaling of spin fluctuations after a series of quenches to the critical Hamiltonian of a long-range Ising model. With systems of up to 50 spins, we show that the amplitude and timescale of the post-quench fluctuations scale with system size with distinct universal critical exponents. While a generic quench can lead to thermal critical behaviour, we find that a second quench from one critical state to another (i.e. a double quench) results in critical behaviour that does not have an equilibrium counterpart. Our results demonstrate the ability of quantum simulators to explore universal scaling beyond the equilibrium paradigm. © 2023, CC BY.

关键词： Ising model

Utilizing probabilistic entanglement between sensors in quantum networks

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arXiv 2024年

作者： Van Milligen, Emily A. Gagatsos, Christos N. Kaur, Eneet Towsley, Don Guha, Saikat Department of Physics The University of Arizona 1630 East University Boulevard TucsonAZ85721 United States Department of Electrical and Computer Engineering The University of Arizona 1630 East University Boulevard TucsonAZ85721 United States Wyant College of Optical Sciences The University of Arizona 1630 East University Boulevard TucsonAZ85721 United States Program in Applied Mathematics The University of Arizona TucsonAZ85721 United States Cisco Quantum Lab Los Angeles United States College of Computer Science University of Massachusetts AmherstMA United States

One of the most promising applications of quantum networks is entanglement assisted sensing. The field of quantum metrology exploits quantum correlations to improve the precision bound for applications such as precision timekeeping, field sensing, and biological imaging. When measuring multiple spatially distributed parameters, current literature focuses on quantum entanglement in the discrete variable case—and quantum squeezing in the continuous variable case distributed amongst all of the sensors in a given network. However, it can be difficult to ensure all sensors pre-share entanglement of sufficiently high fidelity. This work probes the space between fully entangled and fully classical sensing networks by modeling a star network with probabilistic entanglement generation that is attempting to estimate the average of local parameters. The quantum Fisher information is used to determine which protocols best utilize entanglement as a resource for different network conditions. It is shown that without entanglement distillation there is a threshold fidelity below which classical sensing is preferable. For a network with a given number of sensors and links characterized by a certain initial fidelity and probability of success, this work outlines when and how to use entanglement, when to store it, and when it needs to be distilled. © 2024, CC BY.

关键词： Quantum entanglement

Toward a generative modeling analysis of CLAS exclusive 2π photoproduction

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arXiv 2023年

作者： Alghamdi, T. Alanazi, Y. Battaglieri, M. Bibrzycki, L. Golda, A.V. Blin, A.N. Hiller Isupov, E.L. Li, Y. Marsicano, L. Melnitchouk, W. Mokeev, V.I. Montaña, G. Pilloni, A. Sato, N. Szczepaniak, A.P. Vittorini, T. Department of Computer Science Old Dominion University NorfolkVA23529 United States Department of Computer Science College of Computer Science and Information Technology Al-Baha University Al-Baha Alaqiq65779 Saudi Arabia Thomas Jefferson National Accelerator Facility Newport NewsVA23606 United States INFN sezione di Genova GenovaI-16146 Italy AGH University of Krakow Faculty of Physics and Applied Computer Science KrakówPL-30-059 Poland Faculty of Physics Lomonosov Moscow State University Moscow119991 Russia Institute for Theoretical Physics Tübingen University TübingenD-72076 Germany Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University Moscow119234 Russia CSSM and CDMPP Department of Physics University of Adelaide 5005 Australia Dipartimento di Scienze Matematiche e Informatiche Scienze Fisiche e Scienze della Terra Università degli Studi di Messina MessinaI-98166 Italy INFN Sezione di Catania CataniaI-95123 Italy Department of Physics Indiana University BloomingtonIN47405 United States Center for Exploration of Energy and Matter Indiana University BloomingtonIN47403 United States Università di Genova GenovaI-16146 Italy

AI-supported algorithms, particularly generative models, have been successfully used in a variety of different contexts. In this work, we demonstrate for the first time that generative adversarial networks (GANs) can be used in high-energy experimental physics to unfold detector effects from multi-particle final states, while preserving correlations between kinematic variables in multidimensional phase space. We perform a full closure test on two-pion photoproduction pseudodata generated with a realistic model in the kinematics of the Jefferson Lab CLAS g11 experiment. The overlap of different reaction mechanisms leading to the same final state associated with the CLAS detector’s nontrivial effects represents an ideal test case for AI-supported analysis. Uncertainty quantification performed via bootstrap provides an estimate of the systematic uncertainty associated with the procedure. The test demonstrates that GANs can reproduce highly correlated multidifferential cross sections even in the presence of detector-induced distortions in the training datasets, and provides a solid basis for applying the framework to real experimental data. Copyright © 2023, The Authors. All rights reserved.

关键词： Generative adversarial networks