Friday, March 08, 2013

Faster than light or instantaneous?

Chinese Physicists Measure Speed of "Spooky Action At a Distance" | MIT Technology Review

I always thought that quantum entanglement was supposed to work instantaneously.  But the fact that they were trying to measure it suggests it must be thought possible that it isn't.  Anyway, the latest result:
They say the results are clear but do not measure the speed of spooky action directly. Instead, the results place a lower bound on how fast it must be. The answer is that it is at least four orders of  magnitude faster than light, and may still turn out to be instantaneous, as quantum mechanics predicts.
And in other light speed news, I see that this paper suggest the speed limit is a result of the quantum vacuum itself:
 We show that the vacuum permeability and permittivity may originate from the magnetization and the polarization of continuously appearing and disappearing fermion pairs. We then show that if we simply model the propagation of the photon in vacuum as a series of transient captures within these ephemeral pairs, we can derive a finite photon velocity. Requiring that this velocity is equal to the speed of light constrains our model of vacuum. Within this approach, the propagation of a photon is a statistical process at scales much larger than the Planck scale. Therefore we expect its time of flight to fluctuate. We propose an experimental test of this prediction.
I have no idea if this (if shown to be true) has any implications for faster than light travel or transfer of information, but it sounds like the sort of idea that might...

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