This article gives an introduction to the multilevel blocking (MLB) approach
to both the fermion and the dynamical sign problem in path-integral Monte Carlo
simulations. MLB is able to substantially relieve the sign problem in many
situations. Besides an exposition of the method, its accuracy and several
potential pitfalls are discussed, providing guidelines for the proper choice of
certain MLB parameters. Simulation results are shown for strongly interacting
electrons in a 2D parabolic quantum dot, the real-time dynamics of several
simple model systems, and the dissipative two-state dynamics (spin-boson
problem).Comment: Review, 20 pages REVTeX, incl. 7 figure
