Published online 13 August 2008 | Nature | doi:10.1038/news.2008.1038

News

Physicists spooked by faster-than-light information transfer

Quantum weirdness even stranger than previously thought.

Two photons can be connected in a way that seems to defy the very nature of space and time, yet still obeys the laws of quantum mechanics.

fibre opticsCan information travel faster than light?PUNCHSTOCK

Physicists at the University of Geneva achieved the weird result by creating a pair of ‘entangled’ photons, separating them, then sending them down a fibre optic cable to the Swiss villages of Satigny and Jussy, some 18 kilometres apart.

The researchers found that when each photon reached its destination, it could instantly sense its twin’s behaviour without any direct communication. The finding does not violate the laws of quantum mechanics, the theory that physicists use to describe the behaviour of very small systems. Rather, it shows just how quantum mechanics can defy everyday expectation, says Nicolas Gisin, the researcher who led the study. “Our experiment just puts the finger where it hurts,” he says. The study is published in Nature1.

Spooky and unsettling

In the everyday world, objects can organize themselves in just a few ways. For example, two people can coordinate their actions by talking directly with each other, or they can both receive instructions from a third source.

“We think space and time are important because that's the kind of monkeys we are.”

Terence Rudolph
Imperial College London

In both these cases, the information is communicated at or below the speed of light, in keeping with Einstein’s axiom that nothing in the Universe can go faster. But quantum mechanics allows for a third way to coordinate information. When two particles are quantum mechanically ‘entangled’ with each other, measuring the properties of one will instantly tell you something about the other. In other words, quantum theory allows two particles to organize themselves at apparently faster-than-light speeds.

Einstein called such behaviour “spooky action at a distance”, because he found it deeply unsettling. He and other physicists clung to the idea that there might be some other way for the particles to communicate with each other at or near the speed of light.

But the new experiment shows that direct communication between the photons (at least as we know it) is simply impossible. The team simultaneously measured several properties of both photons, such as phase, when they arrived at their villages and found that they did indeed have a spooky awareness of each other’s behaviour. On the basis of their measurements, the team concluded that if the photons had communicated, they must have done so at least 100,000 times faster than the speed of light — something nearly all physicists thought would be impossible. In other words, these photons cannot know about each other through any sort of normal exchange of information.

Framed

The team also ruled out other possible reasons for the apparently coordinated behaviour. For example, one could imagine that the photons might have shared information before they left Geneva — but Gisin’s measurements showed that they could not.

A second test ensured that the scientists in the two villages weren’t missing some form of communication thanks to Earth’s motion through space. According to Einstein’s theory of relativity, observers moving at high speeds can have different ‘reference frames’, so that they can potentially get different measurements of the same event. The Geneva results could possibly be explained if the two photons were communicating through a frame of reference that wasn’t readily apparent to the scientists."

mapThe entangled photons were sent to the villages of Satigny and Jussy, some 18 kilometres apart.M-Sat Ltd/SPL

But theoretical calculations2 have shown that performing tests over a full spin of the globe would test all possible reference frames. The team did just that, and they got the same result in all cases.

The bottom line, says Gisin is that “there is just no time for these two photons to communicate”.

The experiment shows that in quantum mechanics at least, some things transcend space-time, says Terence Rudolph, a theorist at Imperial College London. It also shows that humans have attached undue importance to the three dimensions of space and one of time we live in, he argues. “We think space and time are important because that’s the kind of monkeys we are.”

If you are baffled by the result, fear not — you’re not alone. “For me, honestly, it doesn’t make any sense,” says Gisin. “I don’t think we can today claim that we have a good story to tell how this all happens.” He hopes that the work will stimulate theorists to come up with new ways of explaining the spooky effect. 

  • References

    1. Salart, D., Baas, A., Branciard, C., Gisin, N. & Zbinden, H. Nature, 454, 861–864 (2008).
    2. Scarani, V. et al Phys. Lett. A 276, 1-7 (2000) | Article | ChemPort |

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  • #60360

    The effect of measurement between a pair of entangled particles does NOT happen instantaneously. I predict that there is a transference of information between the entangled particles which has a limited velocity equivalent to the velocity of light squared (c^2). Once this prediction is confirmed experimentally it will revolutionize our understanding of the Universe. The offer has been put on the table for anyone to try to disprove me. For further information you can watch my short video here http://www.youtube.com/watch?v=_zgrHxlYTQ0

  • #60361

    The effect of measurement between a pair of entangled particles does NOT happen instantaneously. I predict that there is a transference of information between the entangled particles which has a limited velocity equivalent to the velocity of light squared (c^2). Once this prediction is confirmed experimentally it will revolutionize our understanding of the Universe. The offer has been put on the table for anyone to try to disprove me. For further information you can watch my short video here http://www.youtube.com/watch?v=_zgrHxlYTQ0

  • #61017

    Let's assume for a moment the two photons DO appear to "communicate" their phase shift simultaneously, with no measurable delay. What could cause such an effect? From what I've seen, there are several explanations out there which seem plausible while not pulling the rug out from under 200 years of physics research. 1) The photons are communicating via another dimension, parallel to our own, within which space and time are enfolded, allowing instant communication. Numerous physicists have suggested multiple dimensions beyond what we experience, and even entire universes in those dimensions, aka the 'multiverse'. Objects observed here in our reality "fold" in and out of one or more parallel dimensions, resulting in behavior which seem to violate natural law. 2) Entanglement between seemingly disparate objects at the sub-atomic level is less a "spooky action" and instead a suggestion that the separateness of the two photons is an illusion; the photons are actually one and the same, 'viewed' to be different (recall John Pribram's analogy of a single fish in an aquarium being viewed by cameras mounted in front and to the side-- the images would both 'appear' to be separate while exhibiting an inexplicable, instant awareness of one another's movements. There are more, but I suspect the answer is both simpler and more wonderful than perceived faster-than-light communication.

  • #61116

    technology is passé.this is practice for quantum computer you can buy for $11million. real action is in calcium entanglement. thru vortex manifold the remote atoms could circle w/1000km radius.

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