Quantum Monte Carlo algorithm for arbitrary spin-1/2 Hamiltonians

We present a universal parameter-free quantum Monte Carlo (QMC) algorithm designed to simulate arbitrary spin-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>1</a:mn><a:mo>/</a:mo><a:mn>2</a:mn></a:mrow></a:math> Hamiltonians. To ensure the convergence of the Markov chain to equilibrium for every conceivable case, we devise a clear and simple automated protocol that produces QMC updates that are provably ergodic and satisfy detailed balance. We demonstrate the applicability and versatility of our method by considering several illustrative examples, including the simulation of the XY model on a triangular lattice, the toric code, and random <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mi>k</b:mi></b:math>-local Hamiltonians.