Stochastic averaging in quantum dynamics driven by colored noise: a nonperturbative cluster cumulant approach

Abstract

We present here a nonperturbative cluster cumulant method for generating the stochastically averaged evolution operator U for quantum systems driven by Ornstein-Uhlenbeck colored noise (real and complex). The method induces a boson mapping of the stochastic variable, and interprets the averaging as an expectation value with respect to the boson vacuum |0_B>. The evolution of the mapped operator U_B, written in a factorized cluster expansion, is governed by a deterministic Hamiltonian H_B defined in an expanded Fock space. The apparatus of our recently developed multireference coupled cluster formalism is invoked to solve the resultant cluster cumulant equations. Numerical applications are presented to illustrate the formalism.