Mitigating spikes in fermion Monte Carlo methods by reshuffling measurements.

We propose a method to mitigate heavy-tailed distributions in fermion quantum Monte Carlo simulations originating from zeros of the fermion determinant. In this case, the second moment of the observables might not be well defined, and we show that by merely changing the synchronization between local updates and computation of observables, one can reduce the prefactor of the heavy-tailed distribution, thus substantially suppressing statistical fluctuations of observables. We also show that the average, or the first moment, is well defined and hence is independent on our measuring scheme.