  A continuous-time formulation of the Diffusion Monte Carlo method for lattice
models is presented. In its simplest version, without the explicit use of trial
wavefunctions for importance sampling, the method is an excellent tool for
investigating quantum lattice models in parameter regions close to generalized
Rokhsar-Kivelson points. This is illustrated by showing results for the quantum
dimer model on both triangular and square lattices. The potential energy of two
test monomers as a function of their separation is computed at zero
temperature. The existence of deconfined monomers in the triangular lattice is
confirmed. The method allows also the study of dynamic monomers. A finite
fraction of dynamic monomers is found to destroy the confined phase on the
square lattice when the hopping parameter increases beyond a finite critical
value. The phase boundary between the monomer confined and deconfined phases is
obtained.
