Feshbach projection-operator partitioning for quantum open systems: Stochastic approach

The dynamics of a state of interest coupled to a non-Markovian environment is studied by concatenating the non-Markovian quantum state diffusion equation and the Feshbach projection-operator partitioning technique. An exact one-dimensional stochastic master equation is derived as a general tool for controlling an arbitrary component of the system. We show that the exact one-dimensional stochastic master equation can be efficiently solved beyond the widely adapted second-order master equations. The generality and applicability of this hybrid approach is justified and exemplified by several coherence control problems concerning quantum state protection against leakage and decoherence.