# Berislav Buča: Non-stationary quantum many-body dynamics and synchronization

Source: Mathematical physics seminar

**Berislav Buča (Department of Physics, University of Oxford)**

The assumption that quantum systems relax to a stationary (time-independent) state in the long-time limit underpins statistical physics and much of our intuitive understanding of scientific phenomena. For isolated systems this follows from the eigenstate thermalization hypothesis. When an environment is present theexpectation is that all of phase space is explored, eventually leading to stationarity. However, real-world phenomena, from life to weather patterns are persistently non-stationary. We will discuss simple algebraic conditions that lead to a quantum many-body system never reaching a stationary state, not even a non-equilibrium one. This unusual state of matter characterized by persistent oscillations has been recently called a time crystal. We show that it's existence can be, counter-intuitively, induced through the dissipation itself. We further present necessary and sufficient conditions for the occurrence of persistent oscillations in an open quantum system. Finally, we also discuss how our framework allows for open quantum many-body system displaying complex dynamical behaviour, usually found in macroscopic classical systems, such as synchronization.

References:

B Buca, J Tindall, D Jaksch. Nat. Comms. 10 (1), 1730 (2019)

M Medenjak, B Buca, D Jaksch. arXiv:1905.08266 (2019)

B Buca, D Jaksch. Phys. Rev. Lett. 123, 260401 (2019)

J Tindall, B Buca, J R Coulthard, D Jaksch. Phys. Rev. Lett. 123, 030603 (2019)

J Tindall, C Sanchez Munoz, B Buca, D Jaksch. New J. Phys. 22 013026 (2020)

C Booker, B Buca, D Jaksch. arXiv:2005.05062 (2020)

**Zoom link:**

https://fmf-uni-lj-si.zoom.us/j/93055285938?pwd=WHI5RW5aUlVRU3JYd2RLVHpFbjBhUT09

Meeting ID: 930 5528 5938

Password: 373842