  Particle identity and entanglement are two fundamental quantum properties
that work as major resources for various quantum information tasks. However, it
is still a challenging problem to understand the correlation of the two
properties in the same system. While recent theoretical studies have shown that
the spatial overlap between identical particles is necessary for nontrivial
entanglement, the exact role of particle indistinguishability in the
entanglement of identical particles has never been analyzed quantitatively
before. Here, we theoretically and experimentally investigate the behavior of
entanglement between two bosons as spatial overlap and indistinguishability
simultaneously vary. The theoretical computation of entanglement for generic
two bosons with pseudospins is verified experimentally in a photonic system.
Our results show that the amount of entanglement is a monotonically increasing
function of both quantities. We expect that our work provides an insight into
deciphering the role of the entanglement in quantum networks that consist of
identical particles.
