FILTERED PROPAGATOR FUNCTIONAL FOR ITERATIVE DYNAMICS OF QUANTUM DISSIPATIVE SYSTEMS

We describe a Fortran program which calculates the reduced density mat rix of a one-dimensional quantum mechanical continuous or discrete sys tem coupled to a harmonic dissipative environment. The algorithm is ba sed on Feynman's path integral formulation of time-dependent quantum m echanics. An adiabatic reference is employed to obtain accurate propag ators and the harmonic bath is replaced by an influence functional whi ch is discretized by optimal discrete variable representations. A prop agator functional of statistically significant path segments is constr ucted 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 seri al or parallel mode.