Weak quantum chaos

Kukuljan, Ivan (author), Grozdanov, Sašo (author), Prosen, Tomaž (author)

Out-of-time-ordered correlation functions (OTOCs) are presently being extensively debated as quantifiers of dynamical chaos in interacting quantum many-body systems. We argue that in quantum spin and fermionic systems, where all local operators are bounded, an OTOC of local observables is bounded as well and thus its exponential growth is merely transient. As a better measure of quantum chaos in such systems, we propose, and study, the density of the OTOC of extensive sums of local observables, which can exhibit indefinite growth in the thermodynamic limit. We demonstrate this for the kicked quantum Ising model by using large-scale numerical results and an analytic solution in the integrable regime. In a generic case, we observe the growth of the OTOC density to be linear in time. We prove that this density in general, locally interacting, nonintegrable quantum spin and fermionic dynamical systems exhibits growth that is at most polynomial in time—a phenomenon, which we term weak quantum chaos. In the special case of the model being integrable and the observables under consideration quadratic, the OTOC density saturates to a plateau.

• Language: English
• Keywords: quantum mechanics, quantum chaos
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Author Accepted Manuscript
• Publisher: American Physical Society
• Year: 2017
• Number of pages: Str. 060301-1-060301-6
• Numbering: Vol. 96, iss. 6
• PID: 20.500.12556/RUL-100088
• UDC: 530.145
• ISSN on article: 2469-9950
• DOI: 10.1103/PhysRevB.96.060301
• COBISS.SI-ID: 3179364

Copyright

American Physical Society

• Publication date in RUL: 05.03.2018

Record is a part of a journal

• Title: Physical review
• Publisher: American Physical Society
• ISSN: 2469-9950
• COBISS.SI-ID: 2997348

Secondary language

• Language: Slovenian
• Keywords: kvantna mehanika, teorija kaosa

Projects

• Funder: EC - European Commission
• Funding programme: H2020
• Project number: 694544
• Name: Open many-body non-equilibrium systems
• Acronym: OMNES