  We demonstrate the relevance of complex Gaussian stochastic processes to the
stochastic state vector description of non-Markovian open quantum systems.
These processes express the general Feynman-Vernon path integral propagator for
open quantum systems as the classical ensemble average over stochastic pure
state propagators in a natural way. They are the coloured generalization of
complex Wiener processes in quantum state diffusion stochastic Schrodinger
equations.
