Cluster Monte Carlo Algorithm for the Quantum Rotor Model

We propose a highly efficient "worm" like cluster Monte Carlo algorithm for the quantum rotor model in the link-current representation. We explicitly prove detailed balance for the new algorithm even in the presence of disorder. For the pure quantum rotor model with $μ=0$ the new algorithm yields high precision estimates for the critical point $K_c=0.33305(5)$ and the correlation length exponent $ν=0.670(3)$. For the disordered case, $μ=1/2 \pm 1/2$, we find $ν=1.15(10)$.