Theoretical study of symmetry breaking, exotic phases, and measurement theory in nonequilibrium open-system ultracold atomic gases

2022 Fiscal Year Final Research Report

• Project/Area Number: 18H01145
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: The University of Tokyo
• Principal Investigator: Ueda Masahito 東京大学, 大学院理学系研究科(理学部), 教授 (70271070)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 冷却原子気体 / トポロジー / 非平衡 / 非エルミート

Outline of Final Research Achievements

This study aims at exploring unique phenomena in nonequilibrium open systems which can be realized in ultracold atomic systems subject to controlled introduction of dissipation. We have made a complete classification of topological phases in non-Hermitian systems and found reversal of magnetism due to dissipation. We have also found that the relaxation time scale toward a stationary state depends on not only the spectral gap of the Liouvillean operator but also the localization length of the eigenmodes. Furthermore, we have formulated an effective theory which describes a binary system of Bose-Einstein condensates subject to parallel or antiparallel synthetic gauge fields and used it to investigate collective modes.

Free Research Field

原子・分子・量子エレクトロニクス

Academic Significance and Societal Importance of the Research Achievements

本研究で得られた成果は、基礎学理の観点からは非平衡物理現象の研究のフロンティアを拡大するという観点から意義がある。一方、本研究は、現在盛んに研究されている量子コンピュータのパフォーマンスを決定する主要因の一つであるデコヒーレンス・散逸過程や熱化の問題に対する基本的知見を与えるものと考えられ、この意味で社会的意義を有する。