Two-site reduced density matrix from one- and two-particle Green's functions

Abstract

Strongly correlated electron systems are challenging to calculate, and entanglement in such systems is not widely analyzed. We present an approach that can be used as a postprocessing step for calculating the two-site reduced density matrix and from it entanglement measures such as the mutual information and entanglement negativity. Input is only the one- and two-particle Green's function, which is the output of numerous many-body methods. As an illustration, we present results for a toy model, the Hubbard model on a 2×2 cluster and a six-site ring.