Stochastic wave-function method for non-Markovian quantum master equations

A generalization of the stochastic wave-function method to quantum master e quations which are not in Lindblad form is developed. The proposed stochast ic unraveling is based on a description of the reduced system in a doubled Hilbert space and it is shown that this method is capable of simulating qua ntum master equations with negative transition rates. Non-Markovian effects in the reduced systems dynamics can be treated within this approach by emp loying the time-convolutionless projection operator technique. This ansatz yields a systematic perturbative expansion of the reduced systems dynamics in the coupling strength. Several examples such as the damped Jaynes-Cummin gs model and the spontaneous decay of a two-level system into a photonic ba nd gap are discussed. The power as well as the limitations of the method ar e demonstrated. [S1050-2947(99)08102-0].