  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 post-processing 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 $2\times2$ cluster and a $6$ site ring.
