  Based on recently derived exact stochastic Liouville-von Neumann equations,
several strategies for the efficient simulation of open quantum systems are
developed and tested on the spin-boson model. The accuracy and efficiency of
these simulations is verified for several test cases including both coherent
and incoherent dynamics, involving timescales differing by several orders of
magnitude. Using simulations with a time-dependent field, the time evolution of
coherences in the reduced density matrix is investigated. Even in the case of
weak damping, pronounced preparation effects are found. These indicate hidden
coherence in the interacting system which can only be indirectly observed in
the basis of the reduced quantum dynamics.
