Title: Compressing quantum dynamics

Speaker: Denis Golež , Jozef Stefan Institute

Time: 4:00 pm, 2023-7-20 Thursday

Location: 理科楼C302

Abstract: The nonequilibrium evolution in quantum many-body systems is accompanied by a complexity growth that prevents the exploration of long-time dynamics. We will present a numerical scheme based on nonequilibrium field theory, where we tackle the complexity problem by compressing the evolution on-the-fly. The advance is based on an empirical observation that nonequilibrium Greens functions have a hierarchical low-rank structure making it highly compressible. Moreover, we use the compressed representation to reduce the computational cost in the solution of the nonequilibrium Dyson equation from the previous cubic to quadratic. In the second part of the seminar, we will apply these advances to the dynamics of symmetry-broken states. In the first example, we will show that exciting systems close to the dynamical critical point leads to the chirping of the amplitude mode and provide its interpretation in terms of time-dependent Landau theory. Finally, we will show how to use compressibility to detect dynamical phase transition even when we do not have direct access to the order parameter.

Refs:

[1] Jason Kaye, Denis Golež, SciPost Phys. 10, 091 (2021)

BIO: Denis Golež finished his PhD at the University of Ljubljana in 2014. During his postdoc period, he first joined the group of prof. Philipp Werner (Fribourg, Switzerland) working on the question of photo-doped strongly-correlated systems, like Mott insulators. In 2019, he moved to the Flatiron Institute (New York, USA) as a research scientist working on photo-doped symmetry-broken phases, like antiferromagnets and excitonic insulators, as well as improvements in nonequilibrium Greens function techniques. In 2021, he moved to Jozef Stefan Institute as a senior research scientist.