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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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arXiv 2021年

作者： Utsugi, Takeru Goban, Akihisa Tokunaga, Yuuki Goto, Hayato Aoki, Takao Department of Applied Physics Waseda University 3-4-1 Okubo Shinjuku Tokyo169-8555 Japan Computer & Data Science Laboratories NTT Corporation Musashino180-8585 Japan Corporate Research & Development Center Toshiba Corporation Kanagawa Kawasaki212-8582 Japan

For single-photon generation based on cavity quantum electrodynamics, we investigate a practical model assuming a Gaussian wavepacket. 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 exexternal field. Our formulations provide a practical tool for efficient single-photon generation in a wide variety of experimental platforms. Copyright © 2021, The Authors. All rights reserved.

关键词： Electron beams

Virtual quantum error detection

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arXiv 2023年

作者： Tsubouchi, Kento Suzuki, Yasunari Tokunaga, Yuuki Yoshioka, Nobuyuki 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 Tokyo Musashino180-8585 Japan Wako-shi Saitama351-0198 Japan JST PRESTO 4-1-8 Honcho Kawaguchi Saitama332-0012 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 post-selected 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 operations 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. Copyright © 2023, The Authors. All rights reserved.

关键词： Error detection

Quantum error mitigation for rotation symmetric bosonic codes with symmetry expansion

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arXiv 2022年

作者： Endo, Suguru Suzuki, Yasunari Tsubouchi, Kento Asaoka, Rui Yamamoto, Kaoru Matsuzaki, Yuichiro Tokunaga, Yuuki NTT Computer and Data Science Laboratories NTT Corporation Musashino Tokyo180-8585 Japan Department of Applied Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan Central2 1-1-1 Umezono Ibaraki Tsukuba305-8568 Japan Ibaraki Tsukuba305-8568 Japan

The rotation symmetric bosonic code (RSBC) is a unified framework of practical bosonic codes that have rotation symmetries, such as cat codes and binomial codes. While cat codes achieve the break-even point in which the coherence time of the encoded qubits exceeds that of unencoded qubits, with binomial codes nearly approaching that point, the state preparation fidelity needs to be still improved for practical quantum computing. Concerning this problem, we investigate the framework of symmetry expansion, a class of quantum error mitigation that virtually projects the state onto the noise-free symmetric subspace by exploiting the system’s intrinsic symmetries and post-processing of measurement outcomes. Although symmetry expansion has been limited to error mitigation of quantum states immediately before measurement, we successfully generalize symmetry expansion for state preparation. To implement our method, we use an ancilla qubit and only two controlled-rotation gates via dispersive interactions between the bosonic code states and the ancilla qubit. Interestingly, this method also allows us to virtually prepare the RSBC states only from easy-to-prepare states, e.g., coherent states. We also discuss that the conventional symmetry expansion protocol can be applied to improve the computation fidelity when the symmetries of rotation bosonic codes are unavailable due to low measurement fidelity. By giving comprehensive analytical and numerical arguments regarding the trace distance between the error-mitigated state and the ideal state and the sampling cost of quantum error mitigation, we show that symmetry expansion dramatically suppresses the effect of photon loss. Our novel error mitigation method will significantly enhance computation accuracy in the near-term bosonic quantum computing paradigm. Copyright © 2022, The Authors. All rights reserved.

关键词： Errors

The i.i.d. State Convertibility in the Resource Theory of Asymmetry for Finite Groups and Lie groups

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arXiv 2023年

作者： Shitara, Tomohiro Tajima, Hiroyasu NTT Computer and Data Science Laboratories NTT Corporation 3-9-11 Midori-cho Musashino-shi Tokyo180-8585 Japan Department of Communication Engineering and Informatics University of Electro-Communications 1-5-1 Chofugaoka Chofu Tokyo182-8585 Japan JST PRESTO 4-1-8 Honcho Saitama Kawaguchi332-0012 Japan

In recent years, there has been active research toward understanding the connection between symmetry and physics from the viewpoint of quantum information theory. This approach stems from the resource theory of asymmetry (RTA), a general framework treating quantum dynamics with symmetry, and scopes various fields ranging from the fundamentals of physics, such as thermodynamics and black hole physics, to the limitations of information processing, such as quantum computation, quantum measurement, and error-correcting codes. Despite its importance, in RTA, the resource measures characterizing the asymptotic conversion rate between i.i.d. states are not known except for U(1) and 2. In this letter, we solve this problem for the finite group symmetry and partially solve for the compact Lie group symmetry. For finite groups, we clarify that (1) a set of resource measures characterizes the optimal rate of the exact conversion between i.i.d. states in arbitrary finite groups, and (2) when we consider the approximate conversion with vanishingly small error, we can realize arbitrary conversion rate between almost arbitrary resource states. For Lie group symmetry, we show that the optimal rate of the i.i.d. state conversion with vanishingly small error is bounded by the ratio of the Fisher information matrices. We give a conjecture that the Fisher information matrices also characterize the optimal conversion rate, and illustrate the reasoning. These results are expected to significantly broaden the scope of the application of RTA. Copyright © 2023, The Authors. All rights reserved.

关键词： Fisher information matrix

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

Error Crafting in Mixed Quantum Gate Synthesis

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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

Error-Mitigated Quantum Metrology via Virtual Purification

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Physical Review Letters 2022年第25期129卷 250503-250503页

作者： Kaoru Yamamoto Suguru Endo Hideaki Hakoshima Yuichiro Matsuzaki Yuuki Tokunaga NTT Computer and Data Science Laboratories NTT Corporation Musashino 180-8585 Japan JST PRESTO 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan Research Center for Emerging Computing Technologies National Institute of Advanced Industrial Science and Technology (AIST) Central2 1-1-1 Umezono Tsukuba Ibaraki 305-8568 Japan Center for Quantum Information and Quantum Biology Osaka University 1-2 Machikaneyama Toyonaka 560-0043 Japan NEC-AIST Quantum Technology Cooperative Research Laboratory National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Ibaraki 305-8568 Japan

Quantum metrology with entangled resources aims to achieve sensitivity beyond the standard quantum limit by harnessing quantum effects even in the presence of environmental noise. So far, sensitivity has been mainly discussed from the viewpoint of reducing statistical errors under the assumption of perfect knowledge of a noise model. However, we cannot always obtain complete information about a noise model due to coherence time fluctuations, which are frequently observed in experiments. Such unknown fluctuating noise leads to systematic errors and nullifies the quantum advantages. Here, we propose an error-mitigated quantum metrology that can filter out unknown fluctuating noise with the aid of purification-based quantum error mitigation. We demonstrate that our protocol mitigates systematic errors and recovers superclassical scaling in a practical situation with time-inhomogeneous bias-inducing noise. Our result is the first demonstration to reveal the usefulness of purification-based error mitigation for unknown fluctuating noise, thus paving the way not only for practical quantum metrology but also for quantum computation affected by such noise.

关键词： Quantum algorithms Quantum metrology Quantum sensing Quantum simulation

Resource estimations for the Hamiltonian simulation in correlated electron materials

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Physical Review A 2022年第1期106卷 012612-012612页

作者： Shu Kanno Suguru Endo Takeru Utsumi Tomofumi Tada Department of Materials Science and Engineering Tokyo Institute of Technology 2-12-1 O-okayama Meguro-ku Tokyo 152-8552 Japan NTT Computer and Data Science Laboratories NTT Corporation Musashino 180-8585 Japan JST PRESTO 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan Materials Research Center for Element Strategy Tokyo Institute of Technology 4259 Nagatsuta Midori-ku Yokohama Kanagawa 226-8501 Japan Kyushu University Platform of Inter/Transdisciplinary Energy Research (Q-PIT) Kyushu University Fukuoka 819-0395 Japan

Correlated electron materials, such as superconductors and magnetic materials, are regarded as fascinating targets in quantum computing. However, the quantitative resources, specifically the number of quantum gates and qubits, required to perform a quantum algorithm to simulate correlated electron materials remain unclear. In this study, we estimate the resources required for the Hamiltonian simulation algorithm for correlated electron materials, specifically for organic superconductors, iron-based superconductors, binary transition-metal oxides, and perovskite oxides, using the fermionic swap network. The effective Hamiltonian derived using the ab initio downfolding method is adopted for the Hamiltonian simulation, and a procedure for the resource estimation by using the fermionic swap network for the effective Hamiltonians including the exchange interactions is proposed. For example, in the system for the 102 unit cells, the estimated numbers of gates per Trotter step and qubits are approximately 107 and 103, respectively, on average for the correlated electron materials. Furthermore, our results show that the number of interaction terms in the effective Hamiltonian, especially for the Coulomb interaction terms, is dominant in the gate resources when the number of unit cells constituting the whole system is up to 102, whereas the number of fermionic swap operations is dominant when the number of unit cells is more than 103.

关键词： Quantum algorithms Strongly correlated systems Ab initio calculations Density functional theory

Requirements for fault-tolerant quantum computation with cavity-QED-based atom-atom gates mediated by a photon with a finite pulse length

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arXiv 2021年

作者： Asaoka, Rui Tokunaga, Yuuki Kanamoto, Rina Goto, Hayato Aoki, Takao Computer and Data Science Laboratories NTT Corporation Musashino180-8585 Japan Department of Physics Meiji University Kanagawa Kawasaki214-8571 Japan Corporate Research and Development Center Toshiba Corporation Kanagawa Kawasaki212-8582 Japan Department of Applied Physics Waseda University Shinjuku Tokyo169-8555 Japan

We analyze the requirements for fault-tolerant quantum computation with atom-atom gates based on cavity quantum electrodynamics (cQED) mediated by a photon with a finite pulse length. For short photon pulses, the distorted shape of the reflected pulses from the cQED system is a serious error source. In the previous study by Goto and Ichimura [Phys. Rev. A 82, 032311 (2010)], only the photon loss is minimized without considering the shape distortion to optimize the system parameters. Here we show an improved optimization method to minimize the infidelity due to the shape distortion and the photon losses in a well-balanced manner for the fault-tolerant scheme using probabilistic gates [Phys. Rev. A 80, 040303(R) (2009)]. Under this optimization, we discuss the FTQC requirement for short pulses. Finally, we show that reducing the cavity length is an effective way to reduce the errors of this type of gate in the case of short photon pulses. Copyright © 2021, The Authors. All rights reserved.

关键词： Atoms