The entanglement of indistinguishable particles shared between two parties

Abstract

Using an operational definition we quantify the entanglement, $E_P$, between two parties who share an arbitrary pure state of $N$ indistinguishable particles. We show that $E_P \leq E_M$, where $E_M$ is the bipartite entanglement calculated from the mode-occupation representation. Unlike $E_M$, $E_P$ is {\em super-additive}. For example, $E_P =0$ for any single-particle state, but the state $\ket{1}\ket{1}$, where both modes are split between the two parties, has $E_P = 1/2$. We discuss how this relates to quantum correlations between particles, for both fermions and bosons.