The idea of using a good representation as the zeroth order description of a problem, which
is widely used in perturbation theory and in basis set calculations, is extended to the path
integral formulation of quantum mechanics by constructing improved Feynman propagators.
The best zeroth order propagators cannot be expressed in closed form in general, and are
therefore constructed numerically and stored on one-dimensional grids. Use of improved
propagators in discretized path integral calculations involves a trivial modification of Monte …