On Fermion Entanglement
  Under the historical definition of entanglement, namely that encountered in Einstein--Podolski--Rosen (EPR)--type experiments, it is shown that a particular Slater determinant is entangled. Thus a definition which holds that any Slater determinant is unentangled, found in the literature, is inconsistent with the historical definition. A generalization of the historical definition that embodies its meaning as quantum correlation of observables, in the spirit of the work of many others, but is much simpler and more physically transparent, is presented. 
T. A. Kaplan