Berislav Buca – Niels Bohr Institute, University of Copenhagen

Non-stationary quantum many-body dynamics

Non-stationary processes are special types of non-mixing dynamics characterised by long-time deterministic dynamics. They are ubiquitous in the real world around us – from biological to social phenomena. Likewise, on the quantum level, any successful long circuit depth calculation on a quantum computer is, by definition, non-stationary.
 
Therefore, understanding how non-stationarity emerges from the microscopic quantum laws is of fundamental scientific and technological importance. I will discuss simple algebraic conditions that prevent a quantum many-body system from ever reaching a stationary state, not even a non-equilibrium one. I give several physically relevant examples in both closed and open quantum many-body systems, including an XXZ spin chain in a strong tilt field, a spin-1/2 Creutz ladder with oscillating out-of-time-order correlators, a spin-dephased Fermi-Hubbard model, and a two-component BEC in a lossy optical cavity which was recently experimentally studied.

[1] B Buca, J Tindall, D Jaksch. Nat. Comms. 10 (1), 1730 (2019)
[2] B Buca, D Jaksch. Phys. Rev. Lett. 123, 260401 (2019)
[3] Dogra, et al. Science, 366, 1496 (2019)
[4] M Medenjak, B Buca, and D Jaksch. Phys. Rev. B 102, 041117(R) (2020)
[5] B Buca. Phys. Rev. X 13, 031013 (2023).
[6] B Buca, C Booker, D Jaksch. SciPost Phys. 12, 097 (2022)
[7] B Buca. Phys. Rev. Lett. 128, 100601 (2022).
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