Stochastic simulation of quantum dissipative dynamics

As a system can be separated from its heat bath via a decoupling scheme based on the Hubbard-Stratonovich transformation, the quantum dissipative dynamics is exactly described by the average of the random system moving in the stochastic field induced by the bath. As a test of this stochastic formalism, a direct numerical implementation is employed to simulate the spontaneous decay of a two-state atom. In contrast, the validity of a deterministic algorithm based on the stochastic scheme is investigated. Moreover, a mixed random-deterministic approach is established and its efficiency is exemplified by studying the exact dynamics for the spin-boson model at zero temperature.