  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.
