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Symmetry charges on reduced phase space and BMS algebra

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arXiv 2023年

作者： Han, Muxin Huang, Zichang Tan, Hongwei Department of Physics Florida Atlantic University 777 Glades Road Boca RatonFL33431-0991 United States Institut für Quantengravitation Universität Erlangen-Nürnberg Staudtstr. 7/B2 Erlangen91058 Germany Department of Physics Center for Field Theory and Particle Physics Institute for Nano- electronic devices and Quantum computing Fudan University Shanghai200433 China State Key Laboratory of Surface Physics Fudan University Shanghai200433 China College of Science University of Shanghai for Science and Technology Shanghai200093 China

This paper studies the reduced phase space formulation (relational formalism) of gravity coupling to the Brown-Kuchař dust for asymptotic flat spacetimes. A set of boundary conditions for the asymptotic flatness are formulated for Dirac observables on the reduced phase space. The physical Hamiltonian generates the time translation of the dust clock. We compute the boundary term of the physical Hamiltonian, which is identical to the ADM mass. We construct a set of the symmetry charges on the reduced phase space, which are conserved by the physical Hamiltonian evolution. The symmetry charges generate transformations preserving the asymptotically flat boundary condition. Under the reduced-phase-space Poisson bracket, the symmetry charges form an infinite dimensional Lie algebra AG after adding a central charge. A suitable quotient of AG closely relates to the BMS algebra at spatial infinity by Henneaux and Troessaert. Copyright © 2023, The Authors. All rights reserved.

关键词： Dust

Hierarchical quantum embedding by machine learning for large molecular assemblies

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arXiv 2025年

作者： Bensberg, Moritz Eckhoff, Marco Husistein, Raphael T. Teynor, Matthew S. Sora, Valentina Bro-Jørgensen, William Thomasen, F. Emil Krogh, Anders Lindorff-Larsen, Kresten Solomon, Gemma C. Weymuth, Thomas Reiher, Markus ETH Zurich Department of Chemistry and Applied Biosciences Vladimir-Prelog-Weg 2 Zurich8093 Switzerland University of Copenhagen Department of Chemistry and Nano-Science Center Universitetsparken 5 Copenhagen ØDK-2100 Denmark University of Copenhagen Niels Bohr Institute NNF Quantum Computing Programme Blegdamsvej 17 Copenhagen ØDK-2100 Denmark University of Copenhagen Department of Computer Science Universitetsparken 1 Copenhagen ØDK-2100 Denmark University of Copenhagen Department of Biology Linderstrøm-Lang Centre for Protein Science Ole Maaløes Vej 5 Copenhagen NDK-2200 Denmark University of Copenhagen Center for Health Data Science Department of Public Health Øster Farimagsgade 5 Copenhagen ØDK-1353 Denmark

We present a quantum-in-quantum embedding strategy coupled to machine learning potentials to improve on the accuracy of quantum-classical hybrid models for the description of large molecules. In such hybrid models, relevant structural regions (such as those around reaction centers or pockets for binding of host molecules) can be described by a quantum model that is then embedded into a classical molecular-mechanics environment. However, this quantum region may become so large that only approximate electronic structure models are applicable. To then restore accuracy in the quantum description, we here introduce the concept of quantum cores within the quantum region that are amenable to accurate electronic structure models due to their limited size. Huzinaga-type projection-based embedding, for example, can deliver accurate electronic energies obtained with advanced electronic structure methods. The resulting total electronic energies are then fed into a transfer learning approach that efficiently exploits the higher-accuracy data to improve on a machine learning potential obtained for the original quantum-classical hybrid approach. We explore the potential of this approach in the context of a well-studied protein-ligand complex for which we calculate the free energy of binding using alchemical free energy and non-equilibrium switching simulations. Copyright © 2025, The Authors. All rights reserved.

关键词： Molecules

Analysis of inter-transaction time fluctuations in the cryptocurrency market

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arXiv 2022年

作者： Kwapień, Jaroslaw Wątorek, Marcin Bezbradica, Marija Crane, Martin Mai, Tai Tan Drożdż, Stanislaw Complex Systems Theory Department Institute of Nuclear Physics Polish Academy of Sciences Radzikowskiego 152 Kraków31-342 Poland Faculty of Computer Science and Telecommunications Cracow University of Technology ul. Warszawska 24 Kraków31-155 Poland Adapt Centre School of Computing Dublin City University Glasnevin Dublin Ireland

We analyse tick-by-tick data representing major cryptocurrencies traded on some different cryptocurrency trading platforms. We focus on such quantities like the inter-transaction times, the number of transactions in time unit, the traded volume, and volatility. We show that the inter-transaction times show long-range power-law autocorrelations. These lead to multifractality expressed by the right-side asymmetry of the singularity spectra f (α ) indicating that the periods of increased market activity are characterised by richer multifractality compared to the periods of quiet market. We also show that neither the stretched exponential distribution nor the power-law-tail distribution are able to model universally the cumulative distribution functions of the quantities considered in this work. For each quantity, some data sets can be modeled by the former, some data sets by the latter, while both fail in other cases. An interesting, yet difficult to account for, observation is that parallel data sets from different trading platforms can show disparate statistical properties. Copyright © 2022, The Authors. All rights reserved.

关键词： Electronic money

Exploiting anticommutation in Hamiltonian simulation

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arXiv 2021年

作者： Zhao, Qi Yuan, Xiao Joint Center for Quantum Information and Computer Science University of Maryland College ParkMD20742 United States Center on Frontiers of Computing Studies Department of Computer Science Peking University Beijing100871 China Stanford Institute for Theoretical Physics Stanford University StanfordCA94305 United States

quantum computing can efficiently simulate Hamiltonian dynamics of many-body quantum physics, a task that is generally intractable with classical computers. The hardness lies at the ubiquitous anti-commutative relations of quantum operators, in corresponding with the notorious negative sign problem in classical simulation. Intuitively, Hamiltonians with more commutative terms are also easier to simulate on a quantum computer, and anti-commutative relations generally cause more errors, such as in the product formula method. Here, we theoretically explore the role of anti-commutative relation in Hamiltonian simulation. We find that, contrary to our intuition, anti-commutative relations could also reduce the hardness of Hamiltonian simulation. Specifically, Hamiltonians with mutually anti-commutative terms are easy to simulate, as what happens with ones consisting of mutually commutative terms. Such a property is further utilized to reduce the algorithmic error or the gate complexity in the truncated Taylor series quantum algorithm for general problems. Moreover, we propose two modified linear combinations of unitaries methods tailored for Hamiltonians with different degrees of anti-commutation. We numerically verify that the proposed methods exploiting anti-commutative relations could significantly improve the simulation accuracy of electronic Hamiltonians. Our work sheds light on the roles of commutative and anti-commutative relations in simulating quantum systems. © 2021, CC BY.

关键词： Hamiltonians

Mechanical structure of a spin-1 particle

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Physical Review D 2023年第5期107卷 054007-054007页

作者： June-Young Kim Bao-Dong Sun Dongyan Fu Hyun-Chul Kim Theory Center Jefferson Lab Newport News Virginia 23606 USA Institut für Theoretische Physik II Ruhr-Universität Bochum D-44780 Bochum Germany Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum Matter South China Normal University Guangzhou 510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter Southern Nuclear Science Computing Center South China Normal University Guangzhou 510006 China Helmholtz Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn D-53115 Bonn Germany Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China School of Physical Sciences University of Chinese Academy of Sciences Beijing 101408 China Department of Physics Inha University Incheon 22212 South Korea School of Physics Korea Institute for Advanced Study (KIAS) Seoul 02455 South Korea

We investigate the mechanical structure of a spin-1 particle. Introducing three different frameworks, i.e., the three-dimensional (3D) Breit frame, the two-dimensional (2D) Breit frame, and the 2D infinite momentum frame (equivalently the two-dimensional Drell-Yan frame), we scrutinize the 2D and 3D energy-momentum tensor (EMT) distributions in these frames. We first derive the EMT distributions in the 2D Breit frame by performing the Abel transformation. The mass distribution in the 2D Breit frame contains an additional monopole contribution induced geometrically. The pressure distribution in the 2D Breit frame also gets an induced monopole structure. When the Lorentz boost is carried out, the mass distribution in the 2D infinite-momentum frame acquires the induced dipole term. Similarly, we also have the induced dipole contributions to the pressure and shear-force densities. We visualize the 2D mass distributions when the spin-1 particle is polarized along the x- and z-axes. We observe that the 2D mass distribution in the infinite momentum frame exhibit clearly the induced dipole structure when the spin-1 particle is polarized along the x-axis. We also discuss the strong force fields inside a polarized spin-1 particle.

关键词： Mesons Form factors

Non-zero temperature study of spin 1/2 charmed baryons using lattice gauge theory

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arXiv 2023年

作者： Aarts, Gert Allton, Chris Anwar, M. Naeem Bignell, Ryan Burns, Timothy J. Jäger, Benjamin Skullerud, Jon-Ivar Department of Physics Swansea University SwanseaSA2 8PP United Kingdom & Fondazione Bruno Kessler Strada delle Tabarelle 286 TN Villazzano38123 Italy Quantum Field Theory Center & Danish IAS Department of Mathematics and Computer Science University of Southern Denmark Odense M5230 Denmark Department of Theoretical Physics Hamilton Institute National University of Ireland Maynooth County Kildare Ireland School of Mathematics Trinity College Dublin Ireland

We study the behaviour of spin 1/2 charmed baryons as the temperature increases. We make use of anisotropic lattice QCD simulations with Nf = 2 + 1 dynamical flavours. After determining the positive and negative parity ground state masses at the lowest temperature, we investigate the effect of rising temperature using ratios of thermal lattice correlators with both so-called reconstructed correlators and with simple model correlators. This avoids difficulties associated with non-zero temperature fitting or spectral reconstruction. We find that temperature effects are prominent throughout the hadronic phase for all negative parity channels considered and for some positive parity channels. Subsequently and where possible, we determine the masses of the ground states as a function of temperature. Finally we consider the effect of chiral symmetry restoration and extract an estimate of the pseudocritical temperature from singly charmed baryonic correlators. © 2023, CC BY.

关键词： Correlators

Efficient Simulation of Loop quantum Gravity: A Scalable Linear-Optical Approach

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Physical Review Letters 2021年第2期126卷 020501-020501页

作者： Lior Cohen Anthony J. Brady Zichang Huang Hongguang Liu Dongxue Qu Jonathan P. Dowling Muxin Han Hearne Institute for Theoretical Physics and Department of Physics and Astronomy Louisiana State University Baton Rouge Louisiana 70803 USA Department of Physics Center for Field Theory and Particle Physics and Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai 200433 China State Key Laboratory of Surface Physics Fudan University Shanghai 200433 China Center for Quantum Computing Pengcheng Laboratory Shenzhen 518066 China Department of Physics Florida Atlantic University 777 Glades Road Boca Raton Florida 33431 USA NYU-ECNU Institute of Physics at NYU Shanghai 3663 Zhongshan Road North Shanghai 200062 China CAS-Alibaba Quantum Computing Laboratory CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai 201315 China National Institute of Information and Communications Technology 4-2-1 Nukui-Kitamachi Koganei Tokyo 184-8795 Japan Institut für Quantengravitation Universität Erlangen-Nürnberg Staudtstrasse 7/B2 91058 Erlangen Germany

The problem of simulating complex quantum processes on classical computers gave rise to the field of quantum simulations. quantum simulators solve problems, such as boson sampling, where classical counterparts fail. In another field of physics, the unification of general relativity and quantum theory is one of the greatest challenges of our time. One leading approach is loop quantum gravity (LQG). Here, we connect these two fields and design a linear-optical simulator such that the evolution of the optical quantum gates simulates the spin-foam amplitudes of LQG. It has been shown that computing transition amplitudes in simple quantum field theories falls into the bounded-error quantum polynomial time class, which strongly suggests that computing transition amplitudes of LQG are classically intractable. Therefore, these amplitudes are efficiently computable with universal quantum computers, which are, alas, possibly decades away. We propose here an alternative special-purpose linear-optical quantum computer that can be implemented using current technologies. This machine is capable of efficiently computing these quantities. This work opens a new way to relate quantum gravity to quantum information and will expand our understanding of the theory.

关键词： quantum gravity quantum optics quantum simulation

Ideal-theoretic Explanation of Capacity-achieving Decoding

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arXiv 2021年

作者： Bhandari, Siddharth Harsha, Prahladh Kumar, Mrinal Sudan, Madhu Tata Institute of Fundamental Research Mumbai India Simons Institute for the Theory of Computing BerkeleyCA United States Department of Computer Science & Engineering IIT Bombay Mumbai India School of Engineering and Applied Sciences Harvard University CambridgeMA United States

In this work, we present an abstract framework for some algebraic error-correcting codes with the aim of capturing codes that are list-decodable to capacity, along with their decoding algorithms. In the polynomial ideal framework, a code is specified by some ideals in a polynomial ring, messages are polynomials and the encoding of a message polynomial is the collection of residues of that polynomial modulo the ideals. We present an alternate way of viewing this class of codes in terms of linear operators, and show that this alternate view makes their algorithmic list-decodability amenable to analysis. Our framework leads to a new class of codes that we call affine Folded Reed-Solomon codes (which are themselves a special case of the broader class we explore). These codes are common generalizations of the well-studied Folded Reed-Solomon codes and Univariate Multiplicity codes as well as the less-studied Additive Folded Reed-Solomon codes, and lead to a large family of codes that were not previously known/studied. More significantly our framework also captures the algorithmic list-decodability of the constituent codes. Specifically, we present a unified view of the decoding algorithm for ideal-theoretic codes and show that the decodability reduces to the analysis of the distance of some related codes. We show that a good bound on this distance leads to a capacity-achieving performance of the underlying code, providing a unifying explanation of known capacity-achieving results. In the specific case of affine Folded Reed-Solomon codes, our framework shows that they are efficiently list-decodable up to capacity (for appropriate setting of the parameters), thereby unifying the previous results for Folded Reed-Solomon, Multiplicity and Additive Folded Reed-Solomon codes. © 2021, CC BY-NC-SA.

关键词： Reed-Solomon codes

Crystalline superconductor-semiconductor Josephson junctions for compact superconducting qubits

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arXiv 2025年

作者： Balgley, Jesse Park, Jinho Chu, Xuanjing Arnault, Ethan G. Gustafsson, Martin V. Ranzani, Leonardo Holbrook, Madisen Watanabe, Kenji Taniguchi, Takashi Perebeinos, Vasili Hone, James Fong, Kin Chung Department of Mechanical Engineering Columbia University New YorkNY10027 United States Department of Applied Physics and Mathematics Columbia University New YorkNY10027 United States Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States RTX BBN Technologies Quantum Engineering and Computing Group CambridgeMA02138 United States Department of Physics Columbia University New YorkNY10027 United States National Institute for Materials Science 1-2-1 Sengen Ibaraki Tsukuba305-0044 Japan Department of Electrical Engineering University at Buffalo The State University of New York BuffaloNY14260 United States

The narrow bandgap of semiconductors allows for thick, uniform Josephson junction barriers, potentially enabling reproducible, stable, and compact superconducting qubits. We study vertically stacked van der Waals Josephson junctions with semiconducting weak links, whose crystalline structures and clean interfaces offer a promising platform for quantum devices. We observe robust Josephson coupling across 2–12 nm (3–18 atomic layers) of semiconducting WSe2 and, notably, a crossover from proximity- to tunneling-type behavior with increasing weak link thickness. Building on these results, we fabricate a prototype all-crystalline merged-element transmon qubit with transmon frequency and anharmonicity closely matching design parameters. We demonstrate dispersive coupling between this transmon and a microwave resonator, highlighting the potential of crystalline superconductor-semiconductor structures for compact, tailored superconducting quantum devices. Copyright © 2025, The Authors. All rights reserved.

关键词： Josephson junction devices