On 12/31/2013 7:22 PM, LizR wrote:
On 1 January 2014 13:54, meekerdb <[email protected] <mailto:[email protected]>> wrote:On 12/31/2013 3:24 PM, LizR wrote:On 1 January 2014 12:05, meekerdb <[email protected] <mailto:[email protected]>> wrote: Mark A. Rubin <http://arxiv.org/find/quant-ph/1/au:+Rubin_M/0/1/0/all/0/1> (Submitted on 14 Mar 2001 (v1 <http://arxiv.org/abs/quant-ph/0103079v1>), last revised 10 May 2001 (this version, v2)) Bell's theorem depends crucially on counterfactual reasoning, and is mistakenly interpreted as ruling out a local explanation for the correlations which can be observed between the results of measurements performed on spatially-separated quantum systems. But in fact the Everett interpretation of quantum mechanics, in the Heisenberg picture, provides an alternative local explanation for such correlations. Measurement-type interactions lead, not to many worlds but, rather, to many local copies of experimental systems and the observers who measure their properties. Transformations of the Heisenberg-picture operators corresponding to the properties of these systems and observers, induced by measurement interactions, "label" each copy and provide the mechanism which, e.g., ensures that each copy of one of the observers in an EPRB or GHZM experiment will only interact with the "correct" copy of the other observer(s). The conceptual problem of nonlocality is thus replaced with a conceptual problem of proliferating labels, as correlated systems and observers undergo measurement-type interactions with newly-encountered objects and instruments; it is suggested that this problem may be resolved by considering quantum field theory rather than the quantum mechanics ofparticles.Comments: 18 pages, no figures. Minor changes Subjects: Quantum Physics (quant-ph) Journal reference: Found. Phys. Lett. 14 (2001) 301-322 Report number: WW-10184 Cite as: arXiv:quant-ph/0103079 <http://arxiv.org/abs/quant-ph/0103079> just moves the problem from FTL signaling to FTL labeling. Where is the FTL? I don't recall any suggestion that the "contagion" of entangled systems spreading themeselves in the MWI involves anything FTL.Of course in Hilbert space there's no FTL because the system is just one point and when a measurement is performed it projects the system ray onto a mixture of subspaces; spacetime coordinates are just some labels. I thought there was no FTL in ordinary space, either? (I mean, none required for the MWI?)
Right, but the state in Hilbert space is something like |x1 y1 z1 s1 x2 y2 z2 s2> and when Alice measures s1 at (x1 y1 z1) then s2 is correlated at (x2 y2 z2). As I understand it the MWI advocates say this isn't FTL because this is just selecting out one of infinitely many results |s1 s2>. But the 'selection' has to pair up the spins in a way that violates Bell's inequality.
In fact, it's generally assumed to be very, very STL (unless light itself is involved). At great distances from the laboratory, one imagines that the superposition caused by whatever we might do to cats in boxes would decay to the level of noise, and fail to spread any further.That's an interesting viewpoint - but it's taking spacetime instead of Hilbert space to be the arena. If we take the cat, either alive or dead, and shoot it off into space then, as a signal, it won't fall off as 1/r^2. No, but it will travel STL!
Sure. I was just commenting on the idea that the entanglement has a kind of limited range because of 'background noise'. An interesting idea, similar to one I've had that there is a smallest non-zero probability.
But if you want to get FTL, that's possible if Alice and Bob are near opposite sides of our Hubble sphere when they do their measurements. They are then already moving apart faster than c and will never be able to communicate - with each other, but we, in the middle will eventually receive reports from them so that we can confirm the violation of Bell's inequality.
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