Zero-variance zero-bias principle for observables in quantum Monte Carlo: Application to forces

摘要: A simple and stable method for computing accurate expectation values of observables with variational Monte Carlo (VMC) or diffusion (DMC) algorithms is presented. The basic idea consists in replacing the usual “bare” estimator associated observable by an improved “renormalized” estimator. Using this more averages are obtained: Not only statistical fluctuations reduced but also systematic error (bias) approximate VMC (fixed-node) DMC probability densities. It shown that estimators obey a zero-variance zero-bias property similar to energy local as can be optimized resulting accuracy on may reach remarkable obtained total energies. As important example, we present application our formalism computation forces molecular systems. Cal...