Comment by GolDDranks | Hacker News Reader

Comment by GolDDranks | Hacker News Reader

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You understood correctly that quantum mechanics cannot be based on some hidden variable we haven't or cannot find. (Edit: oops, I re-read your comment and it seems you say the exact opposite thing? The point is that Bell's theorem rules hidden variables OUT. Here's an easily digestible video about this: https://www.youtube.com/watch?v=ZuvK-od647c )

About probability: no one knows. It might be that there is a "wave function collapse" that has a probabilistic outcome. But it might be that there is no such a thing. Quantum mechanics that remain in the "quantum" realm are not probabilistic, it's only when you cross over to the classical world.

So it might be equally well, that the Everett interpretation (so-called "many worlds interpretation") is true, and the probability is something physicist Sean Carroll calls "self-locating uncertainty": https://www.preposterousuniverse.com/blog/2014/07/24/why-pro... That is, there are multiple "yous" that experience different outcomes, and you don't know which branch of the wavefunction you find "yourself" in, which "you" you are.

QM can't be based on LOCAL hidden variables. Hidden variables theories that are explicitly nonlocal are not ruled out. Separately, Superdeterminism eliminates both the requirement for nonlocality and the result that QM is inherently probabilistic.

> QM can't be based on LOCAL hidden variables.

... as long as we assume that the system being measured is uncorrelated with the choices of which measurements to make on it. :-)

Superdeterminism eliminates any requirement(s).

Oh, you are definitely correct. Pardon the inaccuracy.

> You understood correctly that quantum mechanics cannot be based on some hidden variable we haven't or cannot find.

That's not true. The only thing we know is that the above appears to be true, but since we do not actually know the mechanism behind quantum mechanics we will be in this limbo until (if ever) we find the actual rules.

Actually, the power of Bell's theorem is that it applies to any physical theory which attempts to explain observed correlations in experiments on entangled particles. It really does say "No matter what's behind quantum theory, we know it isn't like this".

I do have a small gripe with the above comment, in that Bell's theorem only rules out local hidden variables. Some take the view that Bohmian mechanics is an formulation of quantum theory which employs hidden variables, just explicitly non-local ones.

> I do have a small gripe with the above comment, in that Bell's theorem only rules out local hidden variables. Some take the view that Bohmian mechanics is an formulation of quantum theory which employs hidden variables, just explicitly non-local ones.

Superdeterminism also allows local hidden variable theory without violating Bell's theorem:

> https://en.wikipedia.org/wiki/Superdeterminism

A 2013 interview with the Nobel Laureate Gerard 't Hooft on this topic:

> https://spookyactionbook.com/2013/10/07/does-some-deeper-lev...

A paper by Sabine Hossenfelder and Tim Palmer:

Sabine Hossenfelder and Tim Palmer; Rethinking Superdeterminism

> https://www.frontiersin.org/articles/10.3389/fphy.2020.00139...

In 2016, 't Hooft published a textbook on some specific points of superdeterminism:

Gerard 't Hooft; The Cellular Automaton Interpretation of Quantum Mechanics

> https://link.springer.com/book/10.1007/978-3-319-41285-6

It's true in a sense that you can get around Bell's theorem by supposing that Alice and Bob's mesasurement choices are strongly pre-correlated in a specific way. But then I feel you end up with this sort of bizarre universal conspiracy set up just to make humans believe in quantum theory.

If you have such an objection, you might be interested in section 4 (in particular section 4.1 and 4.2) of the linked paper

Sabine Hossenfelder and Tim Palmer; Rethinking Superdeterminism

> https://www.frontiersin.org/articles/10.3389/fphy.2020.00139...

> Bell's and similar examples that rest on arguments from fine-tuning (or sensitivity, or conspiracy) all implicitly assume that there is no simple way to mathematically express the allowed (or likely) initial states that give rise to the predictions of quantum mechanics.

I mean, this is the crux of it. You'd have to have some convincing way of explaining why states "give rise to the predictions of quantum mechanics" for all possible measurement choices yet to be made by anyone. It still feels conspiratorial to me, having read that whole section! If someone were to show me a simple mathematical expression as defined above, I would be open to it. As far as I can tell, all this article is saying is "maybe it's possible".

> If someone were to show me a simple mathematical expression as defined above, I would be open to it. As far as I can tell, all this article is saying is "maybe it's possible".

Finding such a simple mathematical expression is exactly what research into this direction is for. But obtaining such is rather the end result that one hopes for.

Sure. It's a fine and noble goal, but at this point it just looks... well, as the Wiki article you linked says, "as plausible, and appealing, as belief in ubiquitous alien mind-control".

But there are constraints on those hidden mechanics as well. Not sure hidden variables theory survives these constraints. Can someone more knowledgeable talk on this?

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