Continuous-time auxiliary field Monte Carlo for quantum impurity models
  We present a continuous-time Monte Carlo method for quantum impurity models, which combines a weak-coupling expansion with an auxiliary-field decomposition. The method is considerably more efficient than Hirsch-Fye and free of time discretization errors, and is particularly useful as impurity solver in large cluster dynamical mean field theory (DMFT) calculations. 
Emanuel Gull, Philipp Werner, Olivier Parcollet and Matthias Troyer