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 do more intuitive and simpler-to-compute second-order perturbative approaches 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.
Fruchtman, A., Lambert, N., & Gauger, E. (2016). When do perturbative approaches accurately capture the dynamics of complex quantum systems? Scientific Reports, 6, . https://doi.org/10.1038/srep28204