Evaluations on Some Perturbative Quantum Dissipation Approaches

We compare the results of some perturbative quantum dissipation approaches to the exact linear absorption of two state systems. The considered approximate methods are the so-called complete second-order quantum dissipation theories, in either the chronological ordering prescription or the correlated driving-dissipation form. Analytical results can be derived for the linear absorption of two-state systems. Assessments on their applicability are then made by comparison to the exact results.