I stumbled over this[1] paper recently, in which they report of experimental evidence for the claim made in earlier work[2] that the amount of "waveness" V and "particleness" P of a photon is related to the amount of self-entanglement C via the equation V^2 + P^2 + C^2 = 1.
I found it interesting but being a layman I don't really know if it brings anything useful to the table, so to speak, in terms of improving our understanding of QM. Does it?