研究者基本情報

• 博士(理学), 北海道大学, 2019年03月

• https://researchmap.jp/keisuke-asahara

• https://orcid.org/0009-0003-1779-0870
• https://jglobal.jst.go.jp/detail?JGLOBAL_ID=202501006424709116

• 20870786

• https://orcid.org/0009-0003-1779-0870

• 202501006424709116

• 作用素論
• 量子ウォーク

• 自然科学一般, 基礎解析学, 作用素論
• 自然科学一般, 数理物理、物性基礎, 量子ウォーク

研究活動情報

• Two-dimensional quantum central limit theorem by quantum walks
  Keisuke Asahara; Daiju Funakawa; Motoki Seki; Akito Suzuki
  Physical Review A, 113, 2, American Physical Society (APS), 2026年02月23日, ［査読有り］, ［国際誌］
  英語, 研究論文（学術雑誌）, The weak limit theorem (WLT), the quantum analog of the central limit theorem, is foundational to quantum walk (QW) theory. Unlike the universal Gaussian limit of classical walks, deriving analytical forms of the limiting probability density function (PDF) in higher dimensions has remained a challenge since the one-dimensional (1D) Konno distribution was established. Previous explicit PDFs for two-dimensional (2D) models were limited to specific cases whose fundamental nature was unclear. This paper resolves this long-standing gap by introducing the notion of maximal speed v max as a critical parameter. We demonstrate that all previous 2D solutions correspond to a degenerate regime where v max = 1 . We then present the first exact analytical representation of the limiting PDF for the physically richer, unexplored regime v max < 1 of a general class of 2D two-state QWs. Our result reveals 2D Konno functions that govern these dynamics. We establish these as the proper 2D generalization of the 1D Konno distribution by demonstrating their convergence to the 1D form in the appropriate limit. Furthermore, our derivation, based on spectral analysis of the group-velocity map, analytically resolves the singular asymptotic structure: we explicitly determine the caustics loci where the PDF diverges and prove they define the boundaries of the distribution's support. By also providing a closed-form expression for the weight functions, this work offers a complete description of the 2D WLT.
• Spectral mapping theorem of an abstract non-unitary quantum walk
  Keisuke Asahara; Daiju Funakawa; Etsuo Segawa; Akito Suzuki; Noriaki Teranishi
  LINEAR ALGEBRA AND ITS APPLICATIONS, 676, 1, 24, 2023年11月01日, ［査読有り］
  英語, 研究論文（学術雑誌）
• An index theorem for one-dimensional gapless non-unitary quantum walks
  Keisuke Asahara; Daiju Funakawa; Motoki Seki; Yohei Tanaka
  QUANTUM INFORMATION PROCESSING, 20, 9, 2021年09月, ［査読有り］
  英語, 研究論文（学術雑誌）
• Spectral analysis of an abstract pair interaction model
  Keisuke Asahara; Daiju Funakawa
  HOKKAIDO MATHEMATICAL JOURNAL, 50, 1, 1, 54, 2021年02月, ［査読有り］, ［筆頭著者］
  英語, 研究論文（学術雑誌）
• Estimating individual-level optimal causal interventions combining causal models and machine learning models
  Keisuke Kiritoshi; Tomonori Izumitani; Kazuki Koyama; Tomomi Okawachi; Keisuke Asahara; Shohei Shimizu
  Proceedings of The KDD'21 Workshop on Causal Discovery, PMLR, 150, 55, 77, 2021年, ［査読有り］
  英語, 研究論文（国際会議プロシーディングス）

• 2020年04月 - 現在
  日本数学会