https://phys.org/news/2018-06-future-quantum-technologies-exploit-identical.html

The physicists, Rosario Lo Franco and Giuseppe Compagno at the University of Palermo, Italy, have published a paper in which they show the usefulness of identical particle entanglement in a recent issue of Physical Review Letters.

As the physicists explain, in order for two independently prepared, identical particles to be entangled, they must share a region of space in close physical proximity—more technically, the particles' wave functions must spatially overlap, at least partially. If there is no spatial overlap, then there is no entanglement. If there is partial spatial overlap, and measurements are made within the overlap region, then there is conditional entanglement with a certain probability. Only when the wave functions exhibit complete spatial overlap is there always entanglement, though the amount of entanglement depends on both the measurement and the shape of the wave functions.