“After a first system that allows them to verify that they've actually managed to release one, and only one, photon, a condition essential to the success of the experiment, a second device "slices" this particle in two. This splitting allows the researchers to obtain two entangled photon halves.”

I thought a quantum was indivisible. However, one of your latest links talks of splitting the electron, so I guess I could be quite out of date here.

There never was nothing.