Separation of relaxation timescales via strong system-bath coupling: Dissipative three-level system as a case study

TL;DR

This paper analytically shows that strong system-bath coupling in dissipative quantum systems creates two relaxation regimes, with the slow dynamics becoming longer, which can help sustain quantum coherences for quantum state engineering.

Contribution

The study introduces a general analytical framework for understanding relaxation timescales under strong coupling using reaction-coordinate mapping, supported by numerical validation.

Findings

Short-time relaxation accelerates with coupling strength.

Long-time relaxation becomes slower at strong coupling.

Strong coupling can sustain quantum coherences.

Abstract

We analytically demonstrate that strong system-bath coupling separates the relaxation dynamics of a dissipative quantum system into two distinct regimes: a short-time dynamics that, as expected, accelerates with increasing coupling to the environment, and a slow dynamics that, counterintuitively, becomes increasingly prolonged at sufficiently strong coupling. Using the reaction-coordinate polaron-transform mapping, we uncover the general mechanism behind this effect and derive accurate expressions for both relaxation timescales. Numerical simulations confirm our analytical predictions. From a practical perspective, our results suggest that strong coupling to a dissipative bath can autonomously generate and sustain long-lived quantum coherences, offering a promising strategy for bath-engineered quantum state preparation.