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Efficient and high-performance routing of lattice-surgery paths on three-dimensional lattice

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arXiv 2024年

作者： Hamada, Kou Suzuki, Yasunari Tokunaga, Yuuki Department of Mathematical Informatics Graduate School of Information Science and Technology The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-0033 Japan NTT Computer and Data Science Laboratories NTT Corporation Musashino180-8585 Japan JST PRESTO 4-1-8 Honcho Saitama Kawaguchi332-0012 Japan

Encoding logical qubits with surface codes and performing multi-qubit logical operations with lattice surgery is one of the most promising approaches to demonstrate fault-tolerant quantum computing. Thus, a method to efficiently schedule a sequence of lattice-surgery operations is vital for high-performance fault-tolerant quantum computing. A possible strategy to improve the throughput of lattice-surgery operations is splitting a large instruction into several small instructions such as Bell state preparation and measurements and executing a part of them in advance. However, scheduling methods to fully utilize this idea have yet to be explored. In this paper, we propose a fast and high-performance scheduling algorithm for lattice-surgery instructions leveraging this strategy. We achieved this by converting the scheduling problem of lattice-surgery instructions to a graph problem of embedding 3D paths into a 3D lattice, which enables us to explore efficient scheduling by solving path search problems in the 3D lattice. Based on this reduction, we propose a method to solve the path-finding problems, Dijkstra projection. We numerically show that this method reduced the execution time of benchmark programs generated from quantum phase estimation algorithms by 2.7 times compared with a naive method based on greedy algorithms. Our study establishes the relation between the lattice-surgery scheduling and graph search problems, which leads to further theoretical analysis on compiler optimization of fault-tolerant quantum computing. Copyright © 2024, The Authors. All rights reserved.

关键词： Qubits

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

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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

NEO-QEC: Neural Network Enhanced Online Superconducting Decoder for Surface Codes

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arXiv 2022年

作者： Ueno, Yosuke Kondo, Masaaki Tanaka, Masamitsu Suzuki, Yasunari Tabuchi, Yutaka The University of Tokyo Japan Keio University Japan Nagoya University Japan NTT Computer and Data Science Laboratories Japan RIKEN Center for Quantum Computing Japan

Quantum error correction (QEC) is essential for quantum computing to mitigate the effect of errors on qubits, and surface code (SC) is one of the most promising QEC methods. Decoding SCs is the most computational expensive task in the control device of quantum computers (QCs), and many works focus on accurate decoding algorithms for SCs, including ones with neural networks (NNs). Practical QCs also require low-latency decoding because slow decoding leads to the accumulation of errors on qubits, resulting in logical failures. For QCs with superconducting qubits, a practical decoder must be very power-efficient in addition to having high accuracy and low latency. In order to reduce the hardware complexity of QC, we are supposed to decode SCs in a cryogenic environment with a limited power budget, where superconducting qubits operate. In this paper, we propose an NN-based accurate, fast, and low-power decoder capable of decoding SCs and lattice surgery (LS) operations with measurement errors on ancillary qubits. To achieve both accuracy and hardware efficiency of the SC decoder, we apply a binarized NN. We design a neural processing unit (NPU) for the decoder with SFQ-based digital circuits and evaluate it with a SPICE-level simulation. We evaluate the decoder performance by a quantum error simulator for the single logical qubit protection and the minimum operation of LS with code distances up to 13, and it achieves 2.5% and 1.0% accuracy thresholds, respectively. Copyright © 2022, The Authors. All rights reserved.

关键词： Error correction

Projective squeezing for translation symmetric bosonic codes

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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

Stimulated Emission of Superradiant Atoms in Waveguide Quantum Electrodynamics

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Physical Review Applied 2022年第6期18卷 064006-064006页

作者： Rui Asaoka Julio Gea-Banacloche Yuuki Tokunaga Kazuki Koshino Computer and Data Science Laboratories NTT Corporation Musashino 180-8585 Japan Department of Physics University of Arkansas Fayetteville Arkansas 72701 USA College of Liberal Arts and Sciences Tokyo Medical and Dental University Ichikawa 272-0827 Japan

We investigate the stimulated emission of superradiant atoms coupled to a waveguide induced by a coherent-state photon pulse. We provide an analytical result when a short π pulse is incident, which shows that the atoms emit photons coherently into the output pulse, which remains a coherent state in the short pulse limit. An incident pulse is amplified in a phase-preserving manner, where noise is added almost entirely in the phase direction in phase space. This property improves the ratio of the intensity signal to noise after the amplification for sufficiently short pulses. This is a unique feature different from general phase-preserving linear amplifiers, where the signal-to-noise ratio deteriorates in the amplification process. We also discuss the dependence of the photon-emission probability on pulse parameters, such as the pulse area and the duration.

关键词： Quantum control Quantum electrodynamics Quantum information processing with continuous variables Quantum information with atoms & light Quantum networks Spontaneous emission Superradiance & subradiance Waveguides

Speed Limit of Efficient Cavity-Mediated Adiabatic Transfer

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arXiv 2023年

作者： Suenaga, Akinori Utsugi, Takeru Asaoka, Rui Tokunaga, Yuuki Kanamoto, Rina Aoki, Takao Department of Applied Physics Waseda University Okubo Shinjuku Tokyo169-8555 Japan Computer and Data Science Laboratories NTT Corporation Musashino180-8585 Japan Department of Physics Meiji University Kanagawa Kawasaki214-8571 Japan

Cavity-mediated adiabatic transfer (CMAT) is a robust way to perform a two-qubit gate between trapped atoms inside an optical cavity. In the previous study by Goto and Ichimura [H. Goto and K. Ichimura, Phys. Rev. A 77, 013816 (2008).], the upper bound of success probability of CMAT was shown where the operation is adiabatically slow. For practical applications, however, it is crucial to operate CMAT as fast as possible without sacrificing the success probability. In this paper, we investigate the operational speed limit of CMAT conditioned on the success probability being close to the upper bound. In CMAT both the adiabatic condition and the decay of atoms and cavity modes limit the operational speed. We show which of these two conditions more severely limits the operational speed in each cavity-QED parameter region, and find that the maximal operational speed, which is proportional to γ√C, is achieved when the influence of cavity decay is dominant compared to spontaneous emission, where γ and C are spontaneous emission rate and cooperativity. Copyright © 2023, The Authors. All rights reserved.

关键词： Spontaneous emission

Vision Paper for Enabling HCI-AI Digital Healthcare Platform Using AIDAF in Open Healthcare Platform 2030 10th

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Vision Paper for Enabling HCI-AI Digital Healthcare Platform...

10th KES International Conference on Innovation in Medicine and Healthcare, KES-InMed 2022

作者： Masuda, Yoshimasa Ishii, Ryo Shepard, Donald Jain, Rashimi Nakamura, Osamu Toma, Tetsuya The School of Computer Science Carnegie Mellon University PittsburghPA United States NTT Human Informatics Laboratories NTT Corporation Yokosuka-shi Kanagawa Japan Brandeis University BostonMA United States Montclair State University MontclairNJ United States Graduate School of Media and Governance Keio University Kanagawa Japan Graduate School of System Design and Management Keio University Kanagawa Japan School of Management International Digital Design Management Tokyo University of Science Tokyo Japan Institute of NTT Data Management Consulting Inc. Tokyo Japan

ISBN: (纸本)9789811934391

Enterprises and information societies confront crucial challenges currently, while Society 5.0 should contribute to a super smart society, especially for healthcare. Human computer interaction (HCI)—artificial intelligence (AI) digital healthcare platforms are architected to improve the healthcare status of patients with lifestyle-related diseases such as diabetes, and osteoporosis. Furthermore, the above digital platforms are expected to help control costs in the healthcare ecosystem. However, current digital enterprise architecture approaches have not achieved their full potential, especially in the healthcare sector. In this paper, we describe how the adaptive integrated digital architecture framework (AIDAF) with the HCI-AI integrated digital healthcare platform is proposed with a planned case of a university hospital in the Americas. In addition, challenges and future activities for this area are discussed that cover the directions for Society 5.0. We argue that the design of an open healthcare platform "Open Healthcare Platform 2030 - OHP2030" for medical product design and robotics can be developed with AIDAF. The vision of AIDAF applications to enable Society 5.0 in the OHP2030 research initiative is explained. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Human computer interaction

Hardware-Efficient Bosonic Quantum Computing with Detection Capability of Single Photon Loss

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arXiv 2024年

作者： Mori, Yuichiro Matsuzaki, Yuichiro Endo, Suguru Kawabata, Shiro 1-1-1 Umezono Ibaraki Tsukuba305-8568 Japan Department of Electrical Electronic and Communication Engineering Faculty of Science and Engineering Chuo university 1-13-27 Kasuga Bunkyo-ku Tokyo112-8551 Japan NTT Computer and Data Science Laboratories NTT Corporation Tokyo Musashino180-8585 Japan 1-1-1 Umezono Ibaraki Tsukuba305-8568 Japan

Bosonic systems, which have large internal degrees of freedom, offer the potential to create quantum bits with error detection and error correction capabilities. This property is particularly advantageous for near-term quantum computers, where the number of qubits is severely constrained. However, there is still room for improvement in terms of hardware efficiency. They still entail the use of ancillary qubits for various state manipulations, including gate operations. Additionally, complex operations are often required to perform a number of operations. Here, we propose a method to use Kerr non-linear resonators for near-term bosonic quantum computation with the capability of detecting single-photon loss, which requires simple pulse operations without ancillary qubits. By adopting the 02 code, and we can perform the X rotation, Z rotation, and controlled-phase gate for logical qubits. Our results pave the way for practical bosonic quantum computation. Copyright © 2024, The Authors. All rights reserved.

关键词： Qubits

Virtual quantum error detection

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Physical Review A 2023年第4期108卷 042426-042426页

作者： Kento Tsubouchi Yasunari Suzuki Yuuki Tokunaga Nobuyuki Yoshioka Suguru Endo Department of Applied Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan NTT Computer and Data Science Laboratories NTT Corporation Musashino Tokyo 180-8585 Japan Theoretical Quantum Physics Laboratory RIKEN Cluster for Pioneering Research Wako-shi Saitama 351-0198 Japan JST PRESTO 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan

Quantum error correction and quantum error detection necessitate syndrome measurements to detect errors. Performing syndrome measurements for each stabilizer generator can be a significant overhead, considering the fact that the readout fidelity in the current quantum hardware is generally lower than gate fidelity. Here, by generalizing a quantum error mitigation method known as symmetry expansion, we propose a protocol called virtual quantum error detection (VQED). This method virtually allows for evaluating computation results corresponding to postselected quantum states obtained through quantum error detection during circuit execution, without implementing syndrome measurements. Unlike conventional quantum error detection, which requires the implementation of Hadamard test circuits for each stabilizer generator, our VQED protocol can be performed with a constant depth shallow quantum circuit with an ancilla qubit, irrespective of the number of stabilizer generators. Furthermore, for some simple error models, the computation results obtained using VQED are robust against the noise that occurred during the operation of VQED, and our method is fully compatible with other error mitigation schemes, enabling further improvements in computation accuracy and facilitating high-fidelity quantum computing.

关键词： Quantum algorithms Quantum algorithms & computation Quantum error correction Quantum information processing