Wednesday, August 13, 2008

Spooky action 10,000 times FTL. Yawn.

On the one hand, completely boring. Another test of QM is in complete agreement with theory.

On the other hand, this is almost as creepy now as it was when a 2007 Wired magazine article on a 1999 entanglement experiment casually noted that observer-independent reality was up against the possibility of free will. That set me off on my extended review of quantum mechanics; along the way free will seems to have come out ahead of reality.

Not quite as creepy though, because I'm getting used to living in a universe that's infinitely weirder than it seems. Here's the latest edition ...
Quantum weirdness wins again: Entanglement clocks in at 10,000 times faster than light: Scientific American Blog
No matter how many times researchers try, there's just no getting around the weirdness of quantum mechanics.
In the latest attempt, researchers at the University of Geneva in Switzerland tried to determine whether entanglement—the fact that measuring a property of one particle instantly determines the property of another—is actually transmitted by some wave-like signal that's fast but not infinitely fast.
Their test involved a series of measurements on pairs of entangled photons (particles of light) that were generated in Geneva (aerial view at left) and then split apart by optical fiber to two villages 18 kilometers (11 miles) apart where the team had set up photon detectors. (In 2007, researchers transmitted entangled light 144 kilometers between two of the Canary Islands.)
The idea in the new experiment is that the photons in each pair of entangled pair are hitting the distant detectors simultaneously, so there's no time for them to exchange a signal. By comparing results from the two detectors, the researchers determined whether the photons were entangled or not, using a test known as Bell's inequalities.

The photons were indeed entangled, the group reports in Nature. But in reality, no experiment is perfect, so what they end up with is a lower limit on how fast the entanglement could be traveling: 10,000 times the speed of light....
.. It's always conceivable that quantum mechanics might break down (read: show some signs of everyday normalcy) if experimenters could test it the right way. In a 2007 study, researchers in Vienna tested the idea that maybe the instantaneous-ness of entanglement (called nonlocality) was consistent with hidden "variables" that can explain the randomness of quantum measurements. But no dice for that idea...
... Rudolph says we're probably stuck with instantaneous entanglement, which seems impossible to us because we're stuck in everyday space and time. "We need to understand how quantum mechanics sees space and time," he says. "I think there's probably much deeper issues.
Yep, we're stuck.

I recommend Gribbin for a layperson explanation of how bad things are, though his preferred model for understanding entanglement is currently out of fashion (and incompatible with free will).

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