A Multigrid Algorithm for Sampling Imaginary-Time Paths in Quantum Monte   Carlo Simulations
  We describe a novel simulation method that eliminates the slowing-down problem in the Monte Carlo simulations of imaginary-time path integrals near the continuum limit. This method combines a stochastic blocking procedure with the multigrid method to rapidly accelerate the sampling of paths in a quantum Monte Carlo simulation, making its dynamics more ergodic. The effectiveness and efficiency of this method are demonstrated for several one-dimensional quantum systems and compared to other standard and accelerated methods. 
C.H. Mak and Sergei Zakharov