Open system dynamics with non-Markovian quantum trajectories

A non-Markovian stochastic Schrodinger equation for a quantum system couple d to an environment of harmonic oscillators is presented. The ensemble aver age recovers the reduced density matrix without approximation and hence it allows one to determine open system dynamics with strong and non-Markovian environmental effects in a very efficient way. We demonstrate the power of our approach with several illustrative examples. First, we discuss a measur ement-type situation, then a two-state system strongly coupled to a non-Mar kovian environment, exhibiting decays and revivals. Further examples showin g the remarkable features of our new approach to non-Markovian open system dynamics are discussed, for instance, the possibility to shift the "Heisenb erg cut" between system and environment. [S0031-9007(99)08603-2].