Correlation Functions from Quantum Cluster Algorithms: Application to   U(1) Quantum Spin and Quantum Link Models
  We demonstrate how correlation functions for non-diagonal operators can be measured with the loop-cluster algorithm for quantum spin models. We introduce the U(1) quantum link model and present the construction of a cluster algorithm for the model. We further show how an improved estimator for Wilson loops can be realized with the flux-cluster algorithm. 
A. Tsapalis