Journal of Signal Processing
Online ISSN : 1880-1013
Print ISSN : 1342-6230
ISSN-L : 1342-6230
Current issue
Journal of Signal Processing, Vol.29 (2025) No.1 (Editor-in-Chief: Takashi Yahagi)
Displaying 1-3 of 3 articles from this issue
  • Kotaro Murayama, Yoshifumi Moriyama, Ichiro Iimura, Shigeru Nakayama
    2025 Volume 29 Issue 1 Pages 1-10
    Published: January 01, 2025
    Released on J-STAGE: January 01, 2025
    JOURNAL FREE ACCESS

    The variational quantum eigensolver (VQE), a hybrid algorithm combining quantum and classical computing, has attracted significant interest. As an optimizer for VQE, gradient-based methods are frequently used. However, in the presence of complex optimization landscapes, these methods may struggle to search for a globally optimal solution. In this study, we applied the artificial bee colony (ABC) algorithm as an optimizer for VQE, which is a robust swarm intelligence for the optimization of high-dimensional functions. We conducted experiments to investigate the effectiveness of the ABC algorithm in solving number partitioning problems (NPPs) of 4, 5, 6, and 8 sizes. The results showed that an ansatz with fewer blocks yielded superior results for NPPs of these sizes. In this context, “block" refers to a pair of entanglement and rotation layers. The parameters related to the local search in the ABC algorithm, which is the number of iterations to abandon, should be increased in the quantum circuit used in this study. Additionally, the population size should be increased in accordance with the size of the problem to be solved. The objective of this research is to contribute to the selection of optimizers for VQE, with a focus on the problem to be solved, and to contribute to the improvement of VQE performance, which has been a significant area of interest in the noisy intermediate-scale quantum era.

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  • Kazuo Komatsu, Hitoshi Takata
    2025 Volume 29 Issue 1 Pages 11-18
    Published: January 01, 2025
    Released on J-STAGE: January 01, 2025
    JOURNAL FREE ACCESS

    In this paper, we consider a design method of a nonlinear filter using a pseudo-formal linearization based on Chebyshev interpolation. The aims of this design method are the easy synthesis of a nonlinear filter, and the reduction of the computational burden in both linearization and estimation processes. First we divide the given region of state space into some subdomains considering the nonlinearity of the given nonlinear system. Next we piecewisely linearize given nonlinear dynamic and measurement systems by a formal linearization method of Chebyshev interpolation. Then we can apply the steady-state Kalman filter for each linearized system on a subdomain, and smoothly unite each Kalman filter on a subdomain by an automatic choosing function into a single filter on a whole domain. To verify the effectiveness of the presented method, we demonstrate numerical experiments of a nonlinear filter for an electric power system.

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  • -The True Nature of the Mysterious Life and Death of the Cat in Quantum Mechanics!?-
    Nobuo Nagai, Hirofumi Sanada, Takashi Yahagi
    2025 Volume 29 Issue 1 Pages 19-25
    Published: January 01, 2025
    Released on J-STAGE: January 01, 2025
    JOURNAL FREE ACCESS

    Heaviside proposed the telegrapher's equations as an alternative to Maxwell equations and obtained the solution of the telegrapher's equations by the operator method. Indeed, the solution was a one-dimensional wave function. One-dimensional wave equations are partial differential equations and are conventionally solved as initialvalue and boundary-value problems in mathematics. Heaviside's solution was found to be related to the algebraic invariants studied in mathematics in the 19th century. From algebraic invariants, lossless circuits were obtained as Junitary matrix. These research findings are still under study. To utilize the research achievements effectively, the application of lossless circuits obtained from algebraic invariants to quantum physics is one of the issues to be studied in the future.

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