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

TL;DR

This paper demonstrates that simple global spin rotations can exponentially accelerate the relaxation of dissipative quantum spin systems towards their stationary state, offering practical improvements for quantum simulation and computation.

Contribution

It introduces a practical method using global spin rotations to exponentially speed up the approach to stationarity in open quantum systems, extending previous theoretical results.

Findings

Global spin rotations significantly reduce relaxation time.

The method is applicable to systems relevant for quantum simulation.

Experimental feasibility demonstrated with trapped atom and ion systems.

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 the recent paper [Carollo et al., Phys. Rev. Lett. 127, 060401 (2021)] it was shown that under certain circumstances it is 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. While 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.