  A generalization of the stochastic wave function method is presented which
allows the unravelling of arbitrary linear quantum master equations which are
not necessarily in Lindblad form and, moreover, the explicit treatment of
memory effects by employing the time-convolutionless projection operator
technique. The crucial point of this construction is the description of the
open system in a doubled Hilbert space, which has already been successfully
used for the computation of multitime correlation functions.
