The feasibility of path integral Monte Carlo ground state calculations with very few beads using a high-order short-time Greens 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.
A quantum Monte Carlo simulation of a system of hard rods in one dimension is presented and discussed. The calculation is exact since the analytical form of the wavefunction is known, and is in excellent agreement with predictions obtained from asymp
totic expansions valid at large distances. The analysis of the static structure factor and the pair distribution function indicates that a solid-like and a gas-like phases exist at high and low densities, respectively. The one-body density matrix decays following a power-law at large distances and produces a divergence in the low density momentum distribution at k=0 which can be identified as a quasi-condensate.
