Exact Non-Markovian Master Equation and Dispersive Probing of   Non-Markovian Process
  For a bosonic (fermionic) open system in a bath with many bosons (fermions) modes, we derive the exact non-Markovian master equation in which the memory effect of the bath is reflected in the time dependent decay rates. In this approach, the reduced density operator is constructed from the formal solution of the corresponding Heisenberg equations. As an application of the exact master equation, we study the active probing of non-Markovianity of the quantum dissipation of a single boson mode of electromagnetic (EM) field in a cavity QED system. The non-Markovianity of the bath of the cavity is explicitly reflected by the atomic decoherence factor. 
Li-Ping Yang, C. Y. Cai, D. Z. Xu, Wei-Min Zhang, and C. P. Sun
quant-ph