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Comment by zkhalique | Hacker News Reader

I am still not so sure that Bell's theorem and subsequent experiments really do rule out hidden variables.

After all, if I split a coin down the middle and took the two halves to different sides of a continent, it wouldn't be surprising if one was found to be heads and one found to be tails.

It would also not be surprising that if I then repainted one of the halves, the other half would be independent of the repainting and the "entanglement" would be broken.

The difference could be simply in that quantum particles behave differently than having only TWO sides to them, like a coin. But the principle is the same ... that the FTL "spooky" communication never happens even between two particles -- rather, they are correlated because were taken from the SAME PLACE at the same time. We just don't understand how their states work, because they're not just one dimensional states.

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I have seen it explained that Bell's theorem does not, strictly speaking, forbid hidden variables. What is says is that if such hidden variables exist, they are irreducibly quantum, at which point the hidden variables become uninteresting. Recall the historical point of "hidden variables" was to recover classicalness out of the quantum. If the hidden variables are also quantum, they're just pointless elaborations that explain nothing and enable nothing, so why bother with them?

(I've also been quibbled with in replies but I'm not sure if those quibbles are correct.)

Put in more interesting terms, a 2-norm probability system can contain states that are fundamentally inexpressible in a 1-norm probability system. See http://www.scottaaronson.com/democritus/lec9.html for a good discussion on what that means. Viewed from that perspective, Bell's Inequality is all but a trivial result; yes, there really is a way in which "quantum" fundamentally differs from "classical" in a mathematically rigorous manner, despite our culture's casual use of the word "quantum".

Bell tests give more correlation than what you're describing could. That's what makes it "spooky".

For example, there are coordination games which can be won with certainty only by using entanglement (or full communication); where just having pre-shared random variables would not be enough (you'd expect to lose now and then). [1]

It's very hard to give analogies for what entanglement is, because of the tendency for any intuitive mechanism to allow either no coordination or too much coordination.

1: http://twistedoakstudios.com/blog/Post6536_implementing-quan...

You are confusing two different concepts. Splitting the coin into two faces amounts to collapse of the wave function into physical observables. The two halves have been determined.

The idea with Bell Inequalities is that if Alice and Bob are given entangled particles and some predetermined information (local hidden variables) then when Alice and Bob make specific measurements: 1. For local hidden variables, Alice should see results predicted by the whatever she already knows and won't see Bob's actions having any effect on her results. 2. Without local hidden variables, Alice will find (after the fact) that her results are skewed by (correlated to) the measurements Bob made.

Exhaustive experimentation has been consistent with #2.

Interesting idea and not one I'd ever really considered. Then again, I'm barely even a layman regarding this stuff so there are probably a lot of things I haven't considered yet.

Look into the kochen-specker theorem. It is much easier to grasp the non-classicalness of it than Bell's IMO.

It is important to note here that Einstein was not being translated from German properly into English. 'Spuk' has a meaning akin to spook in the sense of a remote observer; Rather than 'spooky', which is an adjective relating to ghosts.

There are also a lot of assumptions in the no-cloning theorem regarding the nature of quantum operators: that they absolutely must be linear and unitary. This is certainly not the case for research into invisibility or stealth technology, where non-linear optics are standard.

Lastly, the epistemological nature of hidden variables is the property which rules them out. They are referred to as extraneous variables in every other field of science. This has caused problems of overfitting; Biologists can hold excessive faith in Hidden Markov Models. When you dissect Bell's theorem in terms of raw mathematics, it is technically a restatement of the triangle inequality within probability spaces; So it just ensures that the transitive property holds for the variables of a functional system.

> It is important to note here that Einstein was not being translated from German properly into English. 'Spuk' has a meaning akin to spook in the sense of a remote observer; Rather than 'spooky', which is an adjective relating to ghosts.

Einstein's "spukhaft" is very much an adjective relating to the activity of ghosts. If you translate it as "magical", you're not losing much of its meaning.

Spooks can also refer to watchers. There are CIA spooks, idiomatically.

Ghost is translated as geist.

I've never heard this theory before and I don't think it's true. The phrase that Einstein used was "spukhafte Fernwirkung".

Spooks at government agencies are not the spirits of dead people; they are merely remote observers. The word ghost is translated as geist, like in the word 'poltergeist'.

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