Revisiting Aspect’s third experiment
I often wonder how many people who work in quantum foundations have actually read Aspect’s papers describing his famous experiments, particularly his third. In the ensuing years it seems to me that we have tried to bury the implications of non-locality in this paper beneath layers and layers of often impenetrable mathematics and philosophical hyperbole. As Aspect says in the paper,
In this experiment, switching between the two channels occurs about each 10 ns. Since this delay, as well as the lifetime of the intermediate level of the cascade (5 ns), is small compared to L/c (40 ns), a detection event on one side and the corresponding change of orientation on the other side are separated by a spacelike interval.
The italics are mine. The key word here, to me, is corresponding. If the detection event on the one side and the change in orientation on the other are connected in some way and they are spacelike separated, I fail to see how we can so blithely rule out a violation of Einstein causality. While you may beg to differ that it is not “blithe,” it appears as such to an empiricist. If you insist on talking about abstractions like C*-algebras, then you’re opening another can of worms and asking me to believe in the physical existence of these algebras. In other words, the more abstract we get, the more we really need to decide whether these mathematical “objects” truly are real or not. Otherwise, it just looks like a lot of overblown rhetoric to me.