Loop updates for quantum Monte Carlo simulations in the canonical ensemble

TL;DR

This paper introduces a novel non-local update method for quantum Monte Carlo simulations that maintains particle number conservation and symmetry, enabling precise measurements in the canonical ensemble across various physical systems.

Contribution

The paper presents a new non-local updating scheme for quantum Monte Carlo that conserves symmetries and allows exact projections and measurements in the canonical ensemble.

Findings

Enables exact symmetry projection in simulations.

Allows direct evaluation of Green's functions and observables.

Applicable to diverse systems like bosons, nuclei, and superconductors.

Abstract

We present a new non-local updating scheme for quantum Monte Carlo simulations, which conserves particle number and other symmetries. It allows exact symmetry projection and direct evaluation of the equal-time Green's function and other observables in the canonical ensemble. The method is applied to bosonic atoms in optical lattices, neutron pairs in atomic nuclei and electron pairs in ultrasmall superconducting grains.