Emergence of distinct relaxation behaviour and Quantum Regression Theorem in the Ultra-strong Coupling Limit
Statistical Mechanics
2025-08-13 v1 Mesoscale and Nanoscale Physics
High Energy Physics - Theory
Quantum Physics
Abstract
In the framework of open quantum systems, we derive the dynamical equation governing two-time correlation functions in the ultra-strong coupling (USC) regime between the system and its environment. Unlike the case of the standard weak-coupling regime, in the USC case, we find distinct relaxation behavior for two-time correlators depending on the types of the operators involved in the correlation function. Interestingly, the Quantum Regression Theorem (QRT) emerges after the fastest relaxation time-scale, which is governed by the system-bath coupling strength. We exemplify our findings for the dissipative spin-boson model and further find excellent agreement with the numerically exact hierarchical equations of motion (HEOM) method.
Keywords
Cite
@article{arxiv.2508.08378,
title = {Emergence of distinct relaxation behaviour and Quantum Regression Theorem in the Ultra-strong Coupling Limit},
author = {Sakil Khan and Bijay Kumar Agarwalla},
journal= {arXiv preprint arXiv:2508.08378},
year = {2025}
}