  This article provides an introduction to the ideas behind the multilevel
blocking (MLB) approach to the fermion sign problem in path-integral Monte
Carlo simulations, and also gives a detailed discussion of MLB results for
quantum dots. MLB can turn the exponential severity of the sign problem into an
algebraic one, thereby enabling numerically exact studies of otherwise
inaccessible systems. Low-temperature simulation results for up to eight
strongly correlated electrons in a parabolic 2D quantum dot are presented.
