Nested Cluster Algorithm for Frustrated Quantum Antiferromagnets
  Simulations of frustrated quantum antiferromagnets suffer from a severe sign problem. We solve the ergodicity problem of the loop-cluster algorithm in a natural way and apply a powerful strategy to address the sign problem. For the spin 1/2 Heisenberg antiferromagnet on a kagome and on a frustrated square lattice, a nested cluster algorithm eliminates the sign problem for large systems. The method is applicable to general lattice geometries but limited to moderate temperatures. 
M. Nyfeler, F.-J. Jiang, F. K\"ampfer, and U.-J. Wiese