An Infinite Swapping Approach to the Rare-Event Sampling Problem
  We describe a new approach to the rare-event Monte Carlo sampling problem. This technique utilizes a symmetrization strategy to create probability distributions that are more highly connected and thus more easily sampled than their original, potentially sparse counterparts. After discussing the formal outline of the approach and devising techniques for its practical implementation, we illustrate the utility of the technique with a series of numerical applications to Lennard-Jones clusters of varying complexity and rare-event character. 
Nuria Plattner, J. D. Doll, Paul Dupuis, Hui Wang, Yufei Liu, and J.   E. Gubernatis
cond-mat.stat-mech