  The feasibility of path integral Monte Carlo ground state calculations with
very few beads using a high-order short-time Green's function expansion is
discussed. An explicit expression of the evolution operator which provides
dramatic enhancements in the quality of ground-state wave-functions is
examined. The efficiency of the method makes possible to remove the trial wave
function and thus obtain completely model-independent results still with a very
small number of beads. If a single iteration of the method is used to improve a
given model wave function, the result is invariably a shadow-type wave
function, whose precise content is provided by the high-order algorithm
employed.
