Filtered propagator functional for iterative dynamics of quantum dissipative systems

We describe a Fortran program which calculates the reduced density matrix of a one-dimensional quantum mechanical continuous or discrete system coupled to a harmonic dissipative environment. The algorithm is based on Feynman's path integral formulation of time-dependent quantum mechanics. An adiabatic reference is employed to obtain accurate propagators and the harmonic bath is replaced by an influence functional which is discretized by optimal discrete variable representations. A propagator functional of statistically significant path segments is constructed which allows iterative evaluation of the path integral over long time periods. High efficiency is achieved with the aid of sorting and filtering criteria. The appended program is executable in either serial or parallel mode.