LOOP ALGORITHMS FOR MONTE-CARLO SIMULATIONS OF QUANTUM SPIN SYSTEMS

We present a new algorithm for world line Monte Carlo simulations of q uantum spin systems. The algorithm consists of a stochastic pairing an d a stochastic flipping procedure, and the formula for the pairing pro bability is explicitly given for Heisenberg models. As an illustration of the algorithm, we calculated autocorrelation times for simulations of the S = 1 antiferromagnetic Heisenberg chain. The rapid increase i n autocorrelation times which is seen in the conventional world line m ethod as the imaginary-time spacing decreases is eliminated by the pre sent algorithm.