Pseudomodes as an effective description of memory: Non-Markovian   dynamics of two-state systems in structured reservoirs
  We investigate the non-Markovian dynamics of two-state systems in structured reservoirs. We establish a connection between two theoretical quantum approaches, the pseudomodes [B. M. Garraway, Phys. Rev. A 55, 2290 (1997)] and the recently developed non-Markovian quantum jump method [J. Piilo et al., Phys. Rev. Lett. 100, 180402 (2008)]. This connection provides a clear physical picture of how the structured reservoir affects the system dynamics, indicating the role of the pseudomodes as an effective description of the environmental memory. 
L. Mazzola, S. Maniscalco, J. Piilo, K.-A. Suominen, B. Garraway