Accelerating the approach of dissipative quantum spin systems towards stationarity through global spin rotations

Abstract

We consider open quantum systems whose dynamics is governed by a time-independent Markovian Lindblad master equation. Such systems approach their stationary state on a timescale that is determined by the spectral gap of the generator of the master equation dynamics. In a recent paper [Carollo et al., Phys. Rev. Lett. 127, 060401 (2021)] it was shown that under certain circumstances it was possible to exponentially accelerate the approach to stationarity by performing a unitary transformation of the initial state. This phenomenon can be regarded as the quantum version of the so-called Mpemba effect. The transformation of the initial state removes its overlap with the dynamical mode of the open system dynamics that possesses the slowest decay rate and, thus, determines the spectral gap. Whereas this transformation can be exactly constructed in some cases, it is, in practice, challenging to implement. Here we show that even far simpler transformations constructed by a global unitary spin rotation allow to exponentially speed up relaxation. We demonstrate this using simple dissipative quantum spin systems, which are relevant for current quantum simulation and computation platforms based on trapped atoms and ions.