As an aside, congrats to Ars for including a link to the paper (and a DOI) in the article. They always do this, and it's really something that needs to be encouraged elsewhere, especially in newspapers. I think it's fair to say if you don't link to the original paper, what you do shouldn't be counted as "science journalism."
Quantum entanglement shows that reality can't be local
11–20 of 172 posts
Re: Quantum entanglement shows that reality can't be local
#12One thing I've never understood about interpretation of quantum entanglement experiments: Based on what I've learned of these experiments, it seems to me that the least mind-bending interpretation is that the entanglement event results in two particles that have some complementary property k (i.e. one particle has k and the other has ~k) and which one of the two, k or ~k, is had by one of the particles is unknowable…
Re: Quantum entanglement shows that reality can't be local
#13Not a physicist (theoretical or otherwise), but to me the introduction of the concept of "hidden variables" reminds me of the addition of Phlogiston to the body of knowledge. Unless... they're using it as a placeholder for as-yet undiscovered ways that entangled particles can interact, and it's known that it's a placeholder.
"Hidden variables" have been proven to not be a satisfactory explanation for quantum mechanical effects for some time now. http://en.wikipedia.org/wiki/Bell%27s_theorem Though, I should add, what makes this paper interesting is that they try and find loophole around Bell's theorem. This would be a big deal if true.
Local hidden variables. Bell's theorem does not address non-local variables.
Re: Quantum entanglement shows that reality can't be local
#14One thing I've never understood about interpretation of quantum entanglement experiments: Based on what I've learned of these experiments, it seems to me that the least mind-bending interpretation is that the entanglement event results in two particles that have some complementary property k (i.e. one particle has k and the other has ~k) and which one of the two, k or ~k, is had by one of the particles is unknowable…
If you're willing to read through it, there's a Wikipedia article on Bell's theorem: http://en.wikipedia.org/wiki/Bell%27s_theorem
The summary: If you assume simple locality (your k and ~k,) you get different results than what quantum entanglement predicts.
If you want to get rid of the spooky action at a distance, then you need much, much more complicated hidden variables.
Re: Quantum entanglement shows that reality can't be local
#15One thing I've never understood about interpretation of quantum entanglement experiments: Based on what I've learned of these experiments, it seems to me that the least mind-bending interpretation is that the entanglement event results in two particles that have some complementary property k (i.e. one particle has k and the other has ~k) and which one of the two, k or ~k, is had by one of the particles is unknowable…
"However, both particles have the property from their inception, and so no faster-than-light or non-local interpretation should be needed." This is incorrect, both particles have a superposition of k and ~k (to use your terminology). It is not the case that when the wavefunction collapses, we just suddenly find out the "internal state" of the particle. This "internal state" simply does not exist until the wavefunctio…
Even with such a preshared rule book you wouldn't get any FTL communication. You could crate a pair of random number generators this way which will always give the same result. Certainly useful for cryptographic purposes but sadly not direct communication.
Re: Quantum entanglement shows that reality can't be local
#16One thing I've never understood about interpretation of quantum entanglement experiments: Based on what I've learned of these experiments, it seems to me that the least mind-bending interpretation is that the entanglement event results in two particles that have some complementary property k (i.e. one particle has k and the other has ~k) and which one of the two, k or ~k, is had by one of the particles is unknowable…
The way I've usually seen this one presented involves precisely the observation, in that you gain knowledge of the other particle. Of course, saying "because it was always a ~k particle" does not a good explanation make, because that would imply that the resolution of the measurement was somehow predetermined, which is a fancy way of saying that there's a hidden variable.
Not that interpreting all of this to mean that physics is non-local "spooky-action-at-a-distance" is the only viable route, mind.
Consider this: why, exactly, do you believe that when you measure the particle you somehow force it to enter one particular state and therefore the entangled one that's sitting X miles away suddenly enters the opposite one? Are we, humans, sitting outside of quantum mechanics and looking down upon it - and then what we observe is the one true way the world is?
Why would you not, instead, when you measure the particle, entangle the measuring device, and yourself, with the state of the particle? You are, after all, only another part of quantum mechanics the same as anything else.
Re: Quantum entanglement shows that reality can't be local
#17One thing I've never understood about interpretation of quantum entanglement experiments: Based on what I've learned of these experiments, it seems to me that the least mind-bending interpretation is that the entanglement event results in two particles that have some complementary property k (i.e. one particle has k and the other has ~k) and which one of the two, k or ~k, is had by one of the particles is unknowable…
I believe you're talking about "hidden variables" and the argument against it is Bell's Theorem http://en.wikipedia.org/wiki/Bell%27s_theorem
I'm not a physicist and I don't really understand it fully, but I believe this is what you're talking about.
Re: Quantum entanglement shows that reality can't be local
#18The paper is behind a paywall, so I cannot see if they researches addressed this already, but doesn't Everett interpretation preserve locality and not need faster than light propagation? Are the results incompatible, or was it simply disregarded to make the paper look more impactful?
Re: Quantum entanglement shows that reality can't be local
#19This is for me the most interesting part of the whole teleportation / entanglement research. When these papers started coming out we debated the notion of 'faster than light' communication. The counter argument was that you had to move the particles apart and that was constrained by the speed of light. Then the question of "when" the state was resolved was pondered. There were two thought experiments proposed at this…
This doesn't work because there is no moment at which the state is 'known' or 'detangled'. There is no way to tell, by observing one particle, when the other particle was observed. If there was you could send a signal with it, which would be no good.
The universe is a strange place.
Re: Quantum entanglement shows that reality can't be local
#20If you were able to construct a rigid beam 25 million miles long wouldn't you be able to transmit data (push a button) on the other end faster than the speed of light?