Quantum entanglement shows that reality can't be local
arstechnica.com
Quantum entanglement shows that reality can't be local
1–10 of 172 posts
Re: Quantum entanglement shows that reality can't be local
#2That very adorable kitten is way too distracting, and made it very hard to focus on the article.
Re: Quantum entanglement shows that reality can't be local
#3This 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 meetup.
In the first, two highly accurate clocks, separated by enough distance that that speed of light issues were unambiguously resolved by the clocks, which where triggered by the resolution of the quantum state of an entangled particle. Capturing the exact time when the state was known (detangled) on each clock, and then comparing the times on the clocks to determine whether or not it was truly 'instant'.
The second experiment was to set up a 'set' of entangled particles at a distance and resolve only 'some' of them. The set representing 'bits' and the resolved set representing the 'information.'
The question of course is whether or not you can move information this way. Seems like we are getting closer to answering those questions in a definitive way.
I always thought it would be fun to write a short story about someone doing this and discovering that it was the galactic equivalent of 'shortwave' radio and have the alien equivalent of the FCC come out to the planet to arrest the scientists for transmitting without a license :-)
Re: Quantum entanglement shows that reality can't be local
#4One 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 without collapsing the quantum state. However, both particles have the property from their inception, and so no faster-than-light or non-local interpretation should be needed. When the particles are separated to great distance and one is observed to collapse to k, the other must be observed to collapse to ~k because it was always a ~k particle.
Clearly, there's some aspect of the experiments that I don't understand that invalidates this simple interpretation, but I do not know what it is.
Re: Quantum entanglement shows that reality can't be local
#5:/ the more I learn and read about quantum mechanics I'm starting to realize the FTL quantum communication seems to be an SF pipe dream hoped and imagined on some possible theories but they seem to be less than likely. What a PITA.
Ah well, maybe we can still use singularities or something to punch holes in space/time and shoot info through singularity routers :) Though that does seem even farther away then making quantum mech doing communication for us. ah well
Re: Quantum entanglement shows that reality can't be local
#6Not 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.
Re: Quantum entanglement shows that reality can't be local
#7Not 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.
Re: Quantum entanglement shows that reality can't be local
#8This reminds me of the Ansible, a communication device allowing instant or near instant faster-than-light communication. It is seen in many science fiction works and often justified as quantum entanglement in practice.
Re: Quantum entanglement shows that reality can't be local
#9One 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 wavefunction collapse has occurred.
The "no faster than light" doctrine refers specifically to the transfer of information. And no information, in the strictest sense, has been transferred. Think of it like this: try to imagine how you could communicate with someone using quantum entanglement. If you can communicate something, then information has been transferred. But you can't. All you know is that if your particle is k, then theirs is ~k.
Now, you could make up a rule book that says "if my particle is k, then I'll do x, and you'll do y" but that rule book will have to have been shared between both parties before hand, at less than the speed of light.
Edit: should just mention I'm not an expert here, and articles like this are always interesting. Finding loopholes in our conventional understanding. But it's important to know just /what/ our conventional understanding is first to realise why things like this are important.
Re: Quantum entanglement shows that reality can't be local
#10That very adorable kitten is way too distracting, and made it very hard to focus on the article.
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