Jon Heras, Equinox Graphics Ltd.
Scientists have entangled particles in such a way that a future decision can affect the past states of the particles.
updated 4/30/2012 2:25:59 PM ET 2012-04-30T18:25:59

Spooky quantum entanglement just got spookier.




Essentially, the scientists showed that future actions may influence past events, at least when it comes to the messy, mind-bending world of quantum physics.

In the quantum world, things behave differently than they do in the real, macroscopic world we can see and touch around us. In fact, when quantum entanglement was first predicted by the theory of quantum mechanics, Albert Einstein expressed his distaste for the idea, calling it "spooky action at a distance."

The researchers, taking entanglement a step further than ever before, started with two sets of light particles, called photons. [Stunning Photos of the Very Small]

The basic setup goes like this:

Both pairs of photons are entangled, so that the two particles in the first set are entangled with each other, and the two particles in the second set are entangled with each other. Then, one photon from each pair is sent to a person named Victor. Of the two particles that are left behind, one goes to Bob, and the other goes to Alice.

But now, Victor has control over Alice and Bob's particles. If he decides to entangle the two photons he has, then Alice and Bob's photons, each entangled with one of Victor's, also become entangled with each other. And Victor can choose to take this action at any time, even after Bob and Alice may have measured, changed or destroyed their photons.


Such an experiment had first been predicted by physicist Asher Peres in 2000, but had not been realized until now.

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"The way you entangle them is to send them onto a half-silvered mirror," Zeilinger told LiveScience. "It reflects half of the photons, and transmits half. If you send two photons, one to the right and one to the left, then each of the two photons have forgotten where they come from. They lose their identities and become entangled."

Zeilinger said the technique could one day be used to communicate between superfast quantum computers, which rely on entanglement to store information. Such a machine has not yet been created, but experiments like this are a step toward that goal, the researchers say.

"The idea is to create two particle pairs, send one to one computer, the other to another," Zeilinger said. "Then if these two photons are entangled, the computers could use them to exchange information."


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