Path-integral Monte Carlo Simulations without the Sign Problem:   Multilevel Blocking Approach for Effective Actions
  The multilevel blocking algorithm recently proposed as a possible solution to the sign problem in path-integral Monte Carlo simulations has been extended to systems with long-ranged interactions along the Trotter direction. As an application, new results for the real-time quantum dynamics of the spin-boson model are presented. 
R. Egger, L. Muehlbacher, C. H. Mak