When do weak-coupling approaches accurately capture the dynamics of complex quantum systems?

TL;DR

This paper develops an analytical criterion to determine when weak-coupling methods accurately describe the dynamics of complex quantum systems, validated on FMO and spin-boson models.

Contribution

It introduces a simple analytical criterion to assess the validity of weak-coupling approaches in complex quantum dynamics.

Findings

The criterion accurately predicts the applicability of weak-coupling methods.

Validated on FMO complex dynamics and spin-boson model.

Provides a practical tool for choosing appropriate modeling approaches.

Abstract

Understanding the dynamics of higher-dimensional quantum systems embedded in a complex environment remains a significant theoretical challenge. While several approaches yielding numerically converged solutions exist, these are computationally expensive and often provide only limited physical insight. Here we address the question when more intuitive and simpler to compute weak-coupling approaches still provide adequate accuracy. We develop a simple analytical criterion and verify its validity for the case of the much-studied FMO dynamics as well as the canonical spin-boson model.