Overcoming the large-Z problem in quantum monte carlo

The Z6 scaling of computational effort in quantum Monte Carlo (QMC) results in part from a type of critical slowing down. This insight leads to an attack based on acceleration algorithms which modify the dynamics in Langevin-based simulations without changing the steady-state. Configuration space is more rapidly sampled and steps are inherently more decorrelated. A second approach uses a hybrid Metropolis–Green function Monte Carlo method which factors the core and valence wave function, and treats the former variationally with accurate trial functions, and the latter exactly in the presence of the variationally evoling core. This allows separation of the relevant core and valence time scales, and has sped up quantum simulations by over three orders of magnitude.