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Variational secure cloud quantum computing

Physical Review A 2022年第2期105卷 022603-022603页

作者： Yuta Shingu Yuki Takeuchi Suguru Endo Shiro Kawabata Shohei Watabe Tetsuro Nikuni Hideaki Hakoshima Yuichiro Matsuzaki Department of Physics Faculty of Science Division I Tokyo University of Science Shinjuku Tokyo 162-8601 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 NTT Communication Science Laboratories NTT Corporation3-1 Morinosato Wakamiya Atsugi Kanagawa 243-0198 Japan NTT Computer and Data Science Laboratories NTT corporation Musashino Tokyo 180-8585 Japan NEC-AIST Quantum Technology Cooperative Research Laboratory National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Ibaraki 305-8568 Japan

Variational quantum algorithms (VQAs) have been considered to be useful applications of noisy intermediate-scale quantum (NISQ) devices. Typically, in VQAs, a parametrized ansatz circuit is used to generate a trial wave function, and the parameters are optimized to minimize a cost function. On the other hand, blind quantum computing (BQC) has been studied in order to provide a quantum algorithm with security by using cloud networks. A client with a limited ability to perform quantum operations hopes to have access to a quantum computer of a server, and BQC allows the client to use the server's computer without leakage of the client's information (such as input, running quantum algorithms, and output) to the server. However, BQC is designed for fault-tolerant quantum computing, and this requires many ancillary qubits, which may not be suitable for NISQ devices. Here, we propose an efficient way to implement the NISQ computing with guaranteed security for the client. In our architecture, only N+1 qubits are required, under an assumption that the form of ansätze is known to the server, where N denotes the necessary number of the qubits in the original NISQ algorithms. The client only performs single-qubit measurements on an ancillary qubit sent from the server, and the measurement angles can specify the parameters for the ansätze of the NISQ algorithms. The no-signaling principle guarantees that neither parameters chosen by the client nor the outputs of the algorithm are leaked to the server. This work paves the way for new applications of NISQ devices.

关键词： Measurement-based quantum computing Quantum algorithms Quantum networks

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Error Crafting in Mixed Quantum Gate Synthesis

arXiv

引用

arXiv 2024年

作者： Yoshioka, Nobuyuki Akibue, Seiseki Morisaki, Hayata Tsubouchi, Kento Suzuki, Yasunari Department of Applied Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan Saitama Wako-shi351-0198 Japan JST PRESTO 4-1-8 Honcho Saitama Kawaguchi332-0012 Japan International Center for Elementary Particle Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-0034 Japan NTT Communication Science Laboratories NTT Corporation Atsugi243-0198 Japan Graduate School of Engineering Science Osaka University 1-3 Machikaneyama Osaka Toyonaka560-8531 Japan NTT Computer and Data Science Laboratories NTT Corporation Musashino180-8585 Japan

In fault-tolerant quantum computing, errors in unitary gate synthesis is comparable with noise inherent in the gates themselves. While mixed synthesis can suppress such coherent errors quadratically, there is no clear understanding on its remnant error, which hinders us from designing a holistic and practical error countermeasure. In this work, we propose that the classical characterizability of synthesis error can be exploited;remnant errors can be crafted to satisfy desirable properties. We prove that we can craft the remnant error of arbitrary single-qubit unitaries to be Pauli and depolarizing errors, while the conventional twirling cannot be applied in general. For Pauli rotation gates, in particular, the crafting enables us to suppress the remnant error up to cubic order, which results in synthesis with a T-count of log2(1/Ε) up to accuracy of Ε = 10−9. Our work opens a novel avenue in quantum circuit design and architecture that orchestrates error countermeasures. Copyright © 2024, The Authors. All rights reserved.

关键词： Quantum electronics

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Visually Equivalent Light Field 3D for Portable Displays

Visually Equivalent Light Field 3D for Portable Displays

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Conference Record of the IEEE Industry Applications Society Annual Meeting (IAS)

作者： Munekazu Date Shinya Shimizu Susumu Yamamoto NTT Computer and Data Science Laboratories Nippon Telegraph and Telephone Corporation Yokosuka Japan NTT Human Informatics Laboratories Nippon Telegraph and Telephone Corporation Yokosuka Japan

ISBN: (纸本)9781728164021

Highly realistic 3D displays that can reproduce object images to look like physical objects are utilized for natural and correct remote operation in industrial scenes. Therefore, we developed a visually equivalent light field 3D (VELF3D) display that can produce highly realistic, accurate images with a high resolution and a smooth, accurate motion parallax. However, the observation distance is slightly long, and users cannot reach the displayed images. Therefore, we aim to develop a tablet-computer-type VELF3D display that enables users to touch the displayed objects. The display viewpoint density has been increased to achieve a shorter observation distance while maintaining the display depth range. Because higher resolutions are required for a close observation distance and increased display viewpoints, we aimed to improve effective resolution using almost the same pixel pitch display panel. Therefore, we built a prototype that combines a vertical red, green, blue (RGB) stripe display panel and a parallax barrier with subpixel width slits. We confirmed effective resolution improvement by tiny subjective tests. This method also helps increase the depth range of the display when it is observed from a normal distance.

关键词： Three-dimensional displays Image resolution Fluctuations Industry applications Prototypes Tablet computers Light fields

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Logical entanglement distribution between distant 2D array qubits

arXiv

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arXiv 2025年

作者： Maeda, Yuya Suzuki, Yasunari Kobayashi, Toshiki Yamamoto, Takashi Tokunaga, Yuuki Fujii, Keisuke Graduate School of Engineering Science Osaka University 1-3 Machikaneyama Toyonaka Osaka560-8531 Japan NTT Computer and Data Science Laboratories NTT Corporation Musashino180-8585 Japan JST PRESTO 4-1-8 Honcho Kawaguchi Saitama332-0012 Japan Center for Quantum Information and Quantum Biology Institute for Open and Transdisciplinary Research Initiatives Osaka University Japan Center for Quantum Computing RIKEN Wako Saitama351-0198 Japan

Sharing logical entangled pairs between distant quantum nodes is a key process to achieve fault-tolerant quantum computation and communication. However, there is a gap between current experimental specifications and theoretical requirements for sharing logical entangled states while improving experimental techniques. Here, we propose an efficient logical entanglement distribution protocol based on surface codes for two distant 2D qubit array with nearest-neighbor interaction. A notable feature of our protocol is that it allows post-selection according to error estimations, which provides the tunability between the infidelity of logical entanglements and the success probability of the protocol. With this feature, the fidelity of encoded logical entangled states can be improved by sacrificing success rates. We numerically evaluated the performance of our protocol and the trade-off relationship, and found that our protocol enables us to prepare logical entangled states while improving fidelity in feasible experimental parameters. We also discuss a possible physical implementation using neutral atom arrays to show the feasibility of our protocol. © 2025, CC BY.

关键词： Qubits

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Circuit designs for practical-scale fault-tolerant quantum computing

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

引用

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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Efficient Simulation of Leakage Errors in Quantum Error Correcting Codes Using Tensor Network Methods

arXiv

引用

arXiv 2023年

作者： Manabe, Hidetaka Suzuki, Yasunari Darmawan, Andrew S. Graduate School of Engineering Science Osaka University 1-3 Machikaneyama Toyonaka Osaka560-8531 Japan NTT Computer and Data Science Laboratories NTT Corporation Musashino180-8585 Japan JST PRESTO 4-1-8 Honcho Saitama Kawaguchi332-0012 Japan Kyoto University Kitashirakawa Oiwakecho Sakyo-ku Kyoto606-8502 Japan

Leakage errors, in which a qubit is excited to a level outside the qubit subspace, represent a significant obstacle in the development of robust quantum computers. We present a computationally efficient simulation methodology for studying leakage errors in quantum error correcting codes (QECCs) using tensor network methods, specifically Matrix Product States (MPS). Our approach enables the simulation of various leakage processes, including thermal noise and coherent errors, without approximations (such as the Pauli twirling approximation) that can lead to errors in the estimation of the logical error rate. We apply our method to two QECCs: the one-dimensional (1D) repetition code and a thin 3 × d surface code. By leveraging the small amount of entanglement generated during the error correction process, we are able to study large systems, up to a few hundred qudits, over many code cycles. We consider a realistic noise model of leakage relevant to superconducting qubits to evaluate code performance and a variety of leakage removal strategies. Our numerical results suggest that appropriate leakage removal is crucial, especially when the code distance is large. Copyright © 2023, The Authors. All rights reserved.

关键词： Thermal noise

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Stimulated emission from superradiant atoms in waveguide QED

Stimulated emission from superradiant atoms in waveguide QED

引用

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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High-purity single-photon generation based on cavity QED

引用

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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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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Optimal cavity design for minimizing errors in cavity-QED-based atom-photon entangling gates with finite temporal duration

arXiv

引用

arXiv 2022年

作者： Utsugi, Takeru Asaoka, Rui Tokunaga, Yuuki Aoki, Takao Department of Applied Physics Waseda University 3-4-1 Okubo Shinjuku-ku Tokyo169-8555 Japan Computer & Data Science Laboratories NTT Corporation Musashino Tokyo180-8585 Japan

We investigate atom-photon entangling gates based on cavity quantum electrodynamics (QED) for a finite photon-pulse duration, where not only the photon loss but also the temporal mode-mismatch of the photon pulse becomes a severe source of error. We analytically derive relations between cavity parameters, including transmittance, length, and effective cross-sectional area of the cavity, that minimize both the photon loss probability and the error rate due to temporal mode-mismatch by taking it into account as state-dependent pulse delay. We also investigate the effects of pulse distortion using numerical simulations for the case of short pulse duration. We believe that these analyses are the first to suggest that a cavity has an optimal length for the atom-photon gate, providing a fundamental guideline for implementing quantum information processing. Copyright © 2022, The Authors. All rights reserved.

关键词： Atoms

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