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3 party entanglement -Faster than speed of l

slo1
Posts: 4,330
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3/24/2014 2:53:14 PM
Posted: 2 years ago
http://www.sciencedaily.com...

For the first time, physicists at the Institute for Quantum Computing (IQC) at the University of Waterloo have demonstrated the distribution of three entangled photons at three different locations (Alice, Bob and Charlie) several hundreds of metres apart, proving quantum nonlocality for more than two entangled photons.

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To truly test that the hidden local variables are not responsible for the correlation between the three photons, IQC scientists needed the experiment to close what is known as the locality loophole. They achieved this separation of the entangled photons in a way that did not allow for a signal to coordinate the behaviour of the photons, but beaming the entangled photons to trailers parked in fields several hundred meters from their lab.

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First, photon triplets were generated in Resch's lab -- the Alice in the experiment. Then, the first photon was delayed in a 580m optical fibre in the lab while the two other photons travelled up 85m of optical fibre to the rooftop where they were sent through two telescopes. Both photons were then sent to two trailers, Bob and Charlie, about 700m away from the source and from each other.

To maintain the spacelike separate in the experiment, a fourth party, Randy, located in a third trailer randomly selected each of the measurements that Alice was to perform on her photons in the lab.

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The experiment demonstrated the distribution of three entangled particles, which can eventually be used to do more than pairwise communication where only one party can communicate with another. It opens the possibility for multipartite quantum communication protocols, including Quantum Key Distribution (QKD), third man cryptography and quantum secret sharing.
slo1
Posts: 4,330
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3/24/2014 2:55:05 PM
Posted: 2 years ago
Very cool experiment. While the results are not surprising in any way shape or form, the first time entangling three particles and using at three different points for communication is a big advancement to eventually getting to using entanglement as a means of secured communication. Faster than speed of light to boot.