We show how to increase the accuracy of estimates two-point correlation function without sacrificing efficiency. quantify error pair-counts and Landy-Szalay estimator by comparing them with exact reference values. The standard method, using random point sets, is compared geometrically motivated estimators quasi-Monte~Carlo integration. In scales proportionally $1/\sqrt{N_r}$, $N_r$ being number...

We discuss under which conditions multipartite entanglement in mixed quantum states can be characterized only terms of two-point connected correlation functions, as it is the case for pure states. In turn, latter correlations are defined via a suitable combination (disconnected) one- and functions. contrast to states, satisfied turn out rather severe. However, we were able identify some interes...