Comment by joe_the_user | Hacker News Reader

Comment by joe_the_user | Hacker News Reader

Ok, as far as I can tell, this all just a rehash of EPR paradox and the weirdness of the Copenhagen interpretation of QM. The many worlds interpretation resolves everything with full locality. http://en.wikipedia.org/wiki/Many-worlds_interpretation

Just consider, if I take a black marble and a white in hand, shake them up and put them in two boxes so I don't know which marble is in which box and put the two boxes on two sides of the world. Then, when I open one box, I instantly learn the state of the marble in the other. The information is "transmitted" to me "faster than the speed of light" but all because the actual switch event happened in the past. Now, as far as I can, QM entanglement is pretty much the same thing as these boxes. The only weird thing is that the standard interpretation (not the standard theory since it is not necessary for any meaningful measurement), the standard interpretation is that in QM, the equivalent of our marble switch happens when the final measurement happens.

There's nothing in any of this research that involves any concrete evidence whatsoever that faster-than-light information transmittal happens, (feel free to counter-references that), but as far as I've read, all the "transmittal" is "transmittal" the sense of above.

Your description is wildly incomplete. What you've just described is merely ordinary probability theory.

To see the effects of QM, build a device to flip a quantum-mechanical coin. If it comes up heads, put the marbles into the two boxes. If it comes up tails, put the marble into the two boxes in a slightly (but unmeasureably) different way. I.e., whichever procedure you chose, P(white in right)=0.5.

However, when you actually mix in the coin flip, the white marble always in the right box.

This cannot happen in ordinary probability theory, since:

    P(white in right) = P(white in right|heads)P(heads) + P(white in right|tails)P(tails) = 0.25+0.25

Quantum mechanics isn't weird because it has many worlds. Ordinary probability theory does too. Quantum mechanics is weird because those worlds interfere with each other.

Sure, I never claimed to describe all of QM.

However, while are many amazing effects there, I don't see how your particular example of QM weird or others relate make the information transmittal at a distance part. IE, the interference part isn't directly related to the entangled at a distance except it provides a box that you can't look into.

What you are describing is a "hidden variable theory", but it has been shown (See "Bell's Theorem") such a theory cannot be true. QM is stranger than that.

I'm not saying QM's mechanisms are the same boxing marbles. I'm just saying that separating entangle particles isn't just more interesting than boxing marbles, IE, all the modifications that are going interfere with each can be seen as already having happened - which is why QM doesn't allow you to transmit information faster than light.

Fair enough, if it's just an analogy I agree it gives the right intuition.

To be clear, what really happened under MWI is that the wavefunction "branched" into two around the time you created the two particles, and the two branches spearated from each other in configuration space just as the two marbles in your analogy separated in physical space. When you did the measurement, you merely realized which branch you are in.

Where the analogy fails is that the probabilities in QM are inconsistent with there actually having been some hidden choice of marbles made beforehand.

Bell's theorem only shows that local hidden variable theories cannot be true. Non-local hidden variable theories, such as Bohm, are still possible.

This Google Talk from last year provides an argument and interpretation of this that's fairly understandable with a programmer's mindset:

http://www.youtube.com/watch?v=dEaecUuEqfc&sns=em

Could you explain why your example isn't just a hidden variable explanation, which as we know from measurements of Bell's Inequality ( http://en.wikipedia.org/wiki/Bell%27s_theorem ), cannot result in a theory compatible with both locality and the predictions of quantum mechanics.

The example is a hidden variable explanation, simply because you cannot do metaphors for quantum physics using classical physics.

Perhaps another approach will be clearer:

Imagine magical filter goggles, of two types: red and blue. People wearing red goggles can only see other people wearing red goggles, people wearing blue goggles can only see other people wearing blue goggles.

You put a pair of red and blue goggles to each box, then have four people pick a pair of goggles each.

The result is that each person only sees one other person, near the second box, wearing the same colour goggles.

This is more or less how many-worlds works, except instead of both red and blue goggles in the box you have a single pair of goggles that is both red and blue, but not at the same time (decoherence), and thus instead of two people wearing different kind of goggles, you have a single person wearing goggles that are both blue and red.

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