Canonical entanglement for two indistinguishable particle
  We determine the degree of entanglement for two indistinguishable particles based on the two-qubit tensor product structure, which is a framework for emphasizing entanglement founded on observational quantities. Our theory connects canonical entanglement and entanglement based on occupation number for two fermions and for two bosons and shows that the degree of entanglement, based on linear entropy, is closely related to the correlation measure for both the bosonic and fermionic cases. 
Xiao-Guang Wang and Barry C. Sanders