Thursday, August 14, 2008

New Research on Quantum Entanglement

The idea of faster-than-light—even instantaneous—communication has been around for a long time. Pretty much ever since the concept of quantum entanglement was proposed. Albert Einstein, notably, did not believe in such behavior, as his Theory of Relativity showed that faster-than-light travel and even communication were impossible. He mocked quantum entanglement, famously calling it "spooky action at a distance."

Nevertheless, recent studies have confirmed the presence of this "spooky action" and now, for the first time, placed a limit on how quickly it happens. The experiment, conducted in Switzerland, confirmed that the entangled particles had exactly the same properties at the same time, even though they were 11 miles apart. In doing so, the research determined that the minimum speed at which the quantum information could be passing between the two particles was at least 10,000 times the speed of light.

There are several possible explanations, but a great deal of new work would need to be done before we really know what's going on. It's possible that some exotic particle that travels faster than the speed of light (a tachyon) could be emitted by one of the particles and absorbed by the other. Indeed, the theory of tachyons shows that a tachyon with no mass would have an infinite velocity, which in a way means that it would exist completely outside of time, capable of traveling to any (and every) point in the universe instantaneously, and would never exist in time (which is why we have never detected them directly).

It is also possible that nothing is traveling that fast at all, but rather that the act of observing the particles causes their wave functions to collapse, and because the particles are entangled they share the same wave function. If the collapse of the wave function happens instantaneously, then it would happen for both particles at the same time.

In any event, researchers are still quite a ways away from being able to give us a reliable ansible.


Anonymous said...

I liked this comment in the msnbc article:

In a sense, these instantaneous events "seem to happen from outside space-time, in that it's not a story you can tell within space-time," Gisin told LiveScience.

I am wandering if this is another case of incompleteness in the Godel sense....

Matt Metcalf said...

I liked that quote, too, but I'm not sure it's a case of a Godel incompleteness. I think it's more a case of we just don't have the physics (yet) to describe things that are outside space-time.

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