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arXiv 2025年

作者： Yao, Jiacheng Xu, Wei Zhu, Guangxu Yang, Zhaohui Huang, Kaibin Niyato, Dusit National Mobile Communications Research Laboratory Southeast University Nanjing China Purple Mountain Laboratories Nanjing China Shenzhen Research Institute of Big Data Shenzhen China College of Information Science and Electronic Engineering Zhejiang University Hangzhou China Department of Electrical and Electronic Engineering The University of Hong Kong Hong Kong School of Computer Science and Engineering Nanyang Technological University Singapore

Over-the-air computation (AirComp) has recently emerged as a pivotal technique for communication-efficient federated learning (FL) in resource-constrained wireless networks. Though AirComp leverages the superposition property of multiple access channels for computation, it inherently limits its ability to manage inter-task interference in multi-task computing. In this paper, we propose a quantized analog beamforming scheme at the receiver to enable simultaneous multi-task FL. Specifically, inspiring by the favorable propagation and channel hardening properties of large-scale antenna arrays, a targeted analog beamforming method in closed form is proposed for statistical interference elimination. Analytical results reveal that the interference power vanishes by an order of O (1/Nr) with the number of analog phase shifters, Nr, irrespective of their quantization precision. Numerical results demonstrate the effectiveness of the proposed analog beamforming method and show that the performance upper bound of ideal learning without errors can be achieved by increasing the number of low-precision analog phase shifters. Copyright © 2025, The Authors. All rights reserved.

关键词： Multi-task learning

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High-purity single-photon generation based on cavity QED

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Physical Review Research 2025年第1期7卷 013251-013251页

作者： Seigo Kikura Rui Asaoka Masato Koashi Yuuki Tokunaga Department of Applied Physics Graduate School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Faculty of Science and Engineering Waseda University 3-4-1 Okubo Shinjuku-ku Tokyo 169-8585 Japan Computer and Data Science Laboratories NTT Corporation Musashino 180-8585 Japan Photon Science Center Graduate School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan

We propose a scheme for generating a high-purity single photon on the basis of cavity QED. This scheme employs an atom as a four-level system and the structure allows the suppression of the reexcitation process due to the atomic decay, which is known to significantly degrade the single-photon purity in state-of-the-art photon sources using a three-level system. Our analysis shows that the reexcitation probability arbitrarily approaches zero without sacrificing the photon generation probability when increasing the power of a driving laser between two excited states. This advantage is achievable by using current cavity-QED technologies. Our scheme can contribute to developing distributed quantum computation or quantum communication with high accuracy.

关键词： Quantum computers

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Wireless Communication with Flexible Reflector: Joint Placement and Rotation Optimization for Coverage Enhancement

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IEEE Transactions on Wireless Communications 2025年

作者： Lu, Haiquan Yu, Zhi Zeng, Yong Ma, Shaodan Jin, Shi Zhang, Rui Southeast University National Mobile Communications Research Laboratory Nanjing210096 China University of Macau State Key Laboratory of Internet of Things for Smart City Department of Electrical and Computer Engineering China Purple Mountain Laboratories Nanjing211111 China The Chinese University of Hong Kong School of Science and Engineering Shenzhen Research Institute of Big Data Guangdong Shenzhen518172 China National University of Singapore Department of Electrical and Computer Engineering Singapore117583 Singapore

Passive metal reflectors for communication enhancement have appealing advantages such as ultra low cost, zero energy expenditure, maintenance-free operation, long life span, and full compatibility with legacy wireless systems. To unleash the full potential of passive reflectors for wireless communications, this paper proposes a new passive reflector architecture, termed flexible reflector (FR), for enabling the flexible adjustment of beamforming direction via the FR placement and rotation optimization. We consider the multi-FR aided area coverage enhancement and aim to maximize the minimum expected receive power over all locations within the target coverage area, by jointly optimizing the placement positions and rotation angles of multiple FRs. To gain useful insights, the special case of movable reflector (MR) with fixed rotation is first studied to maximize the expected receive power at a target location, where the optimal single-MR placement positions for electrically large and small reflectors are derived in closed-form, respectively. It is shown that the reflector should be placed at the specular reflection point for electrically large reflector. While for area coverage enhancement, the optimal placement is obtained for the single-MR case and a sequential placement algorithm is proposed for the multi-MR case. Moreover, for the general case of FR, joint placement and rotation design is considered for the single-/multi-FR aided coverage enhancement, respectively. Numerical results are presented which demonstrate significant performance gains of FRs over various benchmark schemes under different practical setups in terms of receive power enhancement. © 2002-2012 IEEE.

关键词： Beamforming

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Circuit designs for practical-scale fault-tolerant quantum computing

Circuit designs for practical-scale fault-tolerant quantum c...

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Symposium on VLSI Technology

作者： Yasunari Suzuki Yosuke Ueno Wang Liao Masamitsu Tanaka Teruo Tanimoto NTT Computer & Data Science Laboratories Musashino Tokyo Japan JST RESTO Kawaguchi Saitama Japan Keio University Yokohama Kanagawa Japan The University of Tokyo Bunkyo-ku Tokyo Japan Kyushu University Fukuoka Japan Nagoya University Nagoya Aichi Japan

To demonstrate reliable and scalable quantum computation, we need quantum error correction to reduce its error rates. One of the most challenging parts of implementing quantum error correction is to design error-decoding units, which estimate errors during computation. We estimate the required performances of error-decoding units to run practical-scale quantum algorithms and discuss the directions to satisfy them.

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Unitary-transformed projective squeezing: applications for circuit-knitting and state-preparation of non-Gaussian states

arXiv

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arXiv 2024年

作者： Anai, Keitaro Suzuki, Yasunari Tokunaga, Yuuki Matsuzaki, Yuichiro Takeda, Shuntaro Endo, Suguru Department of Applied Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan NTT Computer and Data Science Laboratories NTT Corporation Musashino Tokyo180-8585 Japan Department of Electrical Electronic and Communication Engineering Faculty of Science and Engineering Chuo University 1-13-27 Kasuga Bunkyo-ku Tokyo112-8551 Japan

Continuous-variable (CV) quantum computing is a promising candidate for quantum computation because it can utilize infinite-dimensional Hilbert space even with one mode and efficiently handle continuous values. Although the photonic platforms have been considered as a leading platform for CV computation, hybrid systems comprising qubits and bosonic modes, e.g., superconducting hardware, have shown significant developments because they can prepare non-Gaussian state by utilizing the nonlinear interaction between the qubits and the bosonic modes. However, the experimentally realizable size of hybrid hardware is currently restricted. Moreover, the fidelity of the non-Gaussian state is still limited. In this work, by developing the projective squeezing method, we establish the formalism for projecting quantum states onto the states that are unitary-transformed from the squeezed vacuum at the expense of the sampling cost. Based on this formalism, we propose methods for simulating larger quantum devices and projecting the state onto one of the typical non-Gaussian states, the cubic phase state, with a higher squeezing level and higher nonlinearity. For practical implementation, we can apply the smeared projector either by linear-combination-of-unitaries or virtual quantum error detection algorithms by leveraging the interactions in hybrid systems of qubits and bosonic modes. We numerically verify the performance of our methods and also show that the effect of photon-loss errors can be suppressed due to projection. Copyright © 2024, The Authors. All rights reserved.

关键词： Qubits

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Multi-temperature charge scaling of ionic solvents: Disparate responses of thermodynamic properties

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Journal of Molecular Liquids 2024年 409卷

作者： Wang, Xiaohui Liu, Meili Li, Yang Zhang, Zuo-yuan Zhuang, Yi Sun, Zhaoxi Beijing Leto Laboratories Co. Ltd. Beijing China Civil and Architectural Engineering University of Miami Coral GablesFL33146 United States College of Information Science and Engineering Shandong Agricultural University Tai'an271018 China School of Data and Computer Science Shandong Women's University Jinan China College of Physical Science and Technology Yangzhou University Yangzhou225009 China Department of Chemistry Johns Hopkins University BaltimoreMD United States Changping Laboratory Beijing102206 China

Charge scaling as a treatment to effectively include the intermolecular charge transfer and polarization effects is widely applied in molecular modelling of ionic solvents. While the charge scaling factor of 0.8 is picked as a generally applicable solution usable in many computational works, in this work based on extremely precise molecular simulations of bulk solvents and nonequilibrium Hamiltonian switching, we highlight the fact that the general 0.8 selection of the charge scaling factor could be a solution specific to the room-temperature condition that most ionic-liquids studies perform. When the environmental condition varies, this ‘general’ recommendation could sometimes lead to huge deviations. The situation is further complicated by the disparate responses of different properties (bulk density and solvation free energy) in the charge scaling space and along the temperature ladder. The driving force triggering the disparate responses could be attributed to the difference between interaction components involved in different thermodynamic properties, i.e., solvent–solvent interactions for bulk density and the additional solute–solvent interaction in the solvation process. A caution hinted by these observations is the necessity of condition- and property-specific parameter adjustment in practical situations. © 2024 Elsevier B.V.

关键词： Ionic liquids

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Stimulated emission from superradiant atoms in waveguide QED

Stimulated emission from superradiant atoms in waveguide QED

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Conference on Lasers and Electro-Optics (CLEO)

作者： Rui Asaoka Julio Gea-Banacloche Yuuki Tokunaga Kazuki Koshino Computer and Data Science Laboratories NTT Corporation Musashino Japan Department of Physics University of Arkansas Fayetteville Arkansas USA College of Liberal Arts and Sciences Tokyo Medical and Dental University Ichikawa Japan

We investigate the stimulated emission from superradiant atoms coupled to a waveguide induced by a coherent-state pulse. We provide the dynamical properties of this system and also evaluate the system as a amplifier.

ISBN: (数字)9781957171050

ISBN: (纸本)9781665466660

关键词： Stimulated emission Atom lasers Waveguide lasers Lasers and electrooptics Electro-optical waveguides

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Full spectrum of novelties in time-dependent urn models

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Physical Review Research 2025年第2期7卷 023127-023127页

作者： Alessandro Bellina Giordano De Marzo Vittorio Loreto Sapienza University of Rome Physics Department I-00185 Rome Italy Centro Ricerche Enrico Fermi I-00184 Rome Italy Sony Computer Science Laboratories–Rome Joint Initiative CREF-SONY Centro Ricerche Enrico Fermi 00184 Rome Italy Complexity Science Hub Vienna 1080 Vienna Austria Center for Data and Methods University of Konstanz Universitaetstrasse 10 78457 Konstanz Germany

Systems driven by innovation, a pivotal force in human society, present various intriguing statistical regularities, from the Heaps' law to logarithmic scaling or somewhat different patterns for the innovation rates. The urn model with triggering (UMT) has been instrumental in modeling these innovation dynamics. Yet a generalization is needed to capture the richer empirical phenomenology. Here we introduce a time-dependent urn model with triggering (TUMT), a generalization of the UMT that crucially integrates time-dependent parameters for reinforcement and triggering to offer a broader framework for modeling innovation in nonstationary systems. Through analytical computation and numerical simulations, we show that the TUMT reconciles various behaviors observed in a broad spectrum of systems from patenting activity to the analysis of gene mutations. We highlight how the TUMT features a “critical” region where both Heaps' and Zipf's laws coexist, for which we compute the exponents.

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Gaussian-wave-packet model for single-photon generation based on cavity quantum electrodynamics under adiabatic and nonadiabatic conditions

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Physical Review A 2022年第2期106卷 023712-023712页

作者： Takeru Utsugi Akihisa Goban Yuuki Tokunaga Hayato Goto Takao Aoki Department of Applied Physics Waseda University 3-4-1 Okubo Shinjuku Tokyo 169-8555 Japan Computer & Data Science Laboratories NTT Corporation Musashino 180-8585 Japan Corporate Research & Development Center Toshiba Corporation Kawasaki Kanagawa 212-8582 Japan

For single-photon generation based on cavity quantum electrodynamics, we investigate a practical model assuming a Gaussian wave packet. This model makes it possible to comprehensively analyze the temporal dynamics of an atom-cavity system with both adiabatic and nonadiabatic conditions using analytical expressions. These results enable us to clarify the relationship between pulse width and maximum success probability over the full range of coupling regimes. We demonstrate how to achieve a high success probability while keeping a short pulse width by optimizing the cavity transmittance parameter and the time-controlled external field. Our formulations provide a practical tool for efficient single-photon generation in a wide variety of experimental platforms.

关键词： Cavity quantum electrodynamics Quantum communication Quantum computation Quantum optics Single photon sources

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Projective squeezing for translation symmetric bosonic codes

arXiv

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arXiv 2024年

作者： Endo, Suguru Anai, Keitaro Matsuzaki, Yuichiro Tokunaga, Yuuki Suzuki, Yasunari NTT Computer and Data Science Laboratories NTT Corporation Tokyo Musashino180-8585 Japan Department of Applied Physics School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan Department of Electrical Electronic and Communication Engineering Faculty of Science and Engineering Chuo university 1-13-27 Kasuga Bunkyo-ku Tokyo112-8551 Japan

The design of translation symmetric bosonic codes, e.g., Gottesmann-Kitaev-Preskill and squeezed cat codes, is robust against photon loss, but the computation accuracy is limited by the available squeezing level. Here, we introduce the projective squeezing (PS) method for computing outcomes for a higher squeezing level by revealing that a linear combination of displacement operators with periodic displacement values constitutes the smeared projector onto the better code space;we also show the analytical relationship between the increased squeezing level and the projection probability. We introduce concrete implementation methods for PS based on linear-combination-of-unitaries and virtual quantum error detection. We also numerically verify our analytical arguments and show that our protocol can mitigate the effect of photon loss. Copyright © 2024, The Authors. All rights reserved.

关键词： Photons

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