Equidistant quenches in few-level quantum systems

TL;DR

This paper investigates relaxation dynamics in few-level open quantum systems, revealing that the previously observed faster uphill relaxation is not universal and depends on system parameters and measures, with a phase diagram illustrating different thermalization behaviors.

Contribution

It demonstrates that equidistant quenches can lead to varied relaxation behaviors in quantum systems, challenging prior assumptions and providing a phase diagram for three-level systems.

Findings

Both faster uphill and downhill relaxations are possible.

Relaxation behavior depends on transition rates and distance measures.

A phase diagram maps different thermalization regimes.

Abstract

A recent work [Phys. Rev. Lett. 125, 110602] showed that among a pair of \textit{thermodynamically} equidistant quenches from a colder and a hotter initial state at a fixed ambient temperature, the relaxation from the colder initial state (\textit{uphill} relaxation) is always faster, for dynamics close to stable minima. Here we show that this is not generically the case for open quantum systems with two or three energy levels. We find that both faster uphill and faster downhill relaxation and symmetric thermal relaxation can be observed in equidistant quenches, depending on the transition rates and the choice of the distance measure used. Furthermore, we obtain a phase diagram in the parameter space for the three-level system corresponding to different thermalization behaviours.