quantum entanglement gets even weirder…

May 26, 2010

Richard Feyman once remarked “if you think you understand quantum mechanics, then you don’t understand quantum mechanics” and virtually every cutting edge experiment in the field seems to prove him right. Well, to be fair, physicists understand quite a bit about quantum mechanics but there are still quite a few mysteries to clarify including that of quantum entanglement. Usually, when you entangle two particles like photons they can be described by the same wave functions even if there are huge distances between them. But how? Do they just instantly mirror each other or is there some sort of delay in when the phenomenon spreads between the entangled photons? That’s what physicists in Switzerland tried to find out with pretty amazing results and as it turns out, while most phenomena in the universe fall in line with the rules of relativity, the quantum world acts as if it’s only begrudgingly obeying them, barely avoiding violating them through technicalities.

After a stream of entangled photons was fired through a fiber optic cables which split them to hit detectors 11 miles apart, the photons were still showing all the signs of entanglement after hitting their detectors. For that to happen, the quantum phenomenon must have been traveling faster than the speed of light. In fact, the math suggests an astonishing 10,000 times the speed of light if not outright instantaneously. But hold on a second, doesn’t that violate special relativity which dictates that nothing can move faster than the speed of light except the fabric of space itself? Well, the catch is that you shouldn’t be able to transmit any sort of information with a quantum phenomenon because you’re only learning about the photon’s states after they hit the detectors, and photons can only travel at the speed of light so the speed of light limit is technically not being violated. So even though we can induce macro objects to exhibit quantum phenomena, there’s a limit to when we can actually collect any information about what’s happening to them.

See: Salart, D., et al. (2008). Testing the speed of ‘spooky action at a distance’ Nature, 454 (7206), 861-864 DOI: 10.1038/nature07121

[ photo illustration by Derek Prospero ]

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  • Jypson

    I believe this was the observation used in the game Mass Effect 2 for FTL point to point communications between galaxies. In their example, a signal was sent through one particle on board their ship, of a set of entangled particles, to the receiving particle at their base. This provided them instant communication no matter where in the universe the ship was. One of the characters asks why every ship doesn’t have this quantum relay device and is answered by the ships artificial intelligence module (man, their version of the future is awesome) that it is cost prohibitive since every ship would have to have thousands of the entangled particles, and they would still be limited to point to point only.

    I guess in the future, they work out the whole Eberhard’s theorem problem…or they use magic :)

  • Greg Fish

    In their example, a signal was sent through one particle on board their ship, of a set of entangled particles, to the receiving particle at their base.

    Yeah, I remember a few sci-fi stories that use the same trick. The problem in the real world though is the fact that you’ll need to actually send those particles and they’ll be limited to the speed of light as they travel. It sounds like a good way to ensure that an entire fleet gets the same transmission, but the craft will only get the actual signal as the photons hit their receivers.

  • Okay, so here’s the deal:

    You create a superhigh density core of matter suspended in a field, both at the sender’s site and the receiving ship’s. Around these, you fire off a stream of entangled photons, which are held in perpetual orbit around the core by the gravitational mass.

    Periodically, you unwind a coded stream of photons from the core, and embed your message into the stream. The receiving ship, of course, is unwinding the same stream to read your message. Granted, this is a finite solution depending on how many photon streams you can separately orbit around your mass core, but it should last a while.

    Now, all you have to do is figure out how to make a tiny black hole for your mass core, to bend the photon stream into a tight enough circle to fit in the communications deck (or on your wrist.) Just one of those simple hurdles to overcome, like creating a wormhole.

    But now you know what they’re up to at the Large Hadron Collider ;-)

  • “If you think you understand quantum mechanics, then you don’t understand quantum mechanics”. Isn’t that Richard Dawkins misquoting Richard Feynman, in “Unweaving the Rainbow”? I know of Feynman’s “I think I can safely say that nobody understands quantum mechanics” which leaves some room for future understanding:-)