Bell's theorem turned a debate about quantum mechanics into a question that experiments could test. Krishna Choudhary and Lester Nare explain how correlations between entangled particles can conflict with bounds imposed by local hidden-variable models. The discussion considers what those results mean for attempts to explain quantum behavior using pre-existing local properties.
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Bell inequalities constrain the correlations allowed by local hidden-variable models.
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Quantum mechanics predicts entangled correlations that can violate those bounds.
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The theorem makes assumptions about the physical world experimentally testable.
367 words · auto-generated from the episode video
24:14variables inside of the universe that create this spooky action at a distance. It's not actually real. Okay, there's actually stuff that's saved when I send a particle this way and its partner the other way. So that when I measure, you know, when I get this like weird correlation, >> that's just because there's something saved and so there's nothing like happening right? >> Belle said, well, not too fast, right? Actually, if if I measure two different observables that can't be measured simultaneously, >> yes, >> for example, the spin this way and the spin the other way, >> um, then I should be able to figure out correlations within these that can only be explained if the wave function is truly collapsing in this weird quantum
24:57way or if the you know many worlds hypothesis is correct or whatever. I mean we don't know which hypothesis of quantum mechanics is correct but we can certainly rule out hidden variables that are local to whatever is happening within these particles. This was huge >> big deal. Let us know in the comments if you think we should care about the quantum function collapsing or not. Are you a many worlds person or not? >> Or do you think it's just a philosophy thing? >> Yes. >> Yeah. >> Yes. Is it meaningful or is it philosophical? We're moving over to 1965 development of density functional therapy, excuse me, theory. >> Yes. Um, this was theoretical physicist Walter Conn. He developed density
25:39functional theory at UC San Diego. Um, effectively before when we were trying to use computers to do quantum simulations, we'd have to worry about every single electron ever >> in our system. Now, that can quickly become super stupid. Okay. Um, and he figured, why don't I replace that multi-dimensional wave function with something like an electron density, which is there's parts of the system that I can assume to be static, right? Like maybe the atoms don't move around that much. So all of the electron clouds can effectively be blurred out electron densities. And then whatever thing is
26:20dynamic, that's the part that I worry about in my simulation. Seems trivial