That is old had.
The basic idea here is that they are using 600 year old light as the random generator.
I was explaining the basic concept for anyone who wasn't familiar with the "spooky action at a distance" phenomenon of quantum mechanics. I would guess there are more than a handful here who didn't or don't know.
The article itself lays it out. You have to. You can't just start from some advanced point with the newest development in the field. At least not unless you're talking to a group of people with that sort of background.
________________________________
"Quantum physics suggests that two so-called entangled particles can maintain a special connection — even at a large distance — such that if one is measured, that instantly tells an experimenter what measuring the other particle will show.
This happens despite the fact neither particle has definite properties until it is measured. That unsettled some physicists, including Einstein, who favoured an alternative explanation: that quantum theory is incomplete, and that the outcomes instead depend on some predetermined, but hidden, variables."