© Photo: Russian Quantum Center
© Photo: Russian Quantum Center
MOSCOW, October 12 – RIA Novosti . Researchers at the Russian Quantum Center learned in practice to recover lost quantum entanglement, which significantly extends the capabilities of quantum communication and quantum cryptography, it said in an article published in the journal Nature Photonics.
The phenomenon of quantum entanglement is the basis of modern quantum technology. This phenomenon, in particular, plays an important role in the secure quantum communication systems – such systems completely eliminate the possibility of undetectable “eavesdropping.” However, the entangled states are very fragile, they are easily broken during transmission due to noise, optical loss.
A group of Russian physicists led by Alexander Lvov learned to restore these quantum link between particles during experiments with the “bloated” optical fiber, in where the signal is fading very quickly due to the insertion of dark glass and a special device that amplifies coming out of it photons.
This procedure consists in mixing almost extinct pulse of the optical fiber with the “auxiliary” photon using a special beam splitter plate which paradoxically reinforces its quantum properties.
This phenomenon discovered Lviv and colleagues in 2002, was named by them quantum catalysis, because “helper” photon, like a catalyst in chemistry, himself no reaction spent, but it changes the state of light in the other channel.
“While this phenomenon seemed no more than a curious phenomenon, what quantum physics a lot. Now it turns out that it is of great practical use – it allows you to restore entanglement of quantum states of light” – says Lviv, whose words the press service of the Roman Catholic Church.
According to him, this work – a step to the creation of quantum repeater – a device capable of reducing the loss of quantum information over fiber optic links. In the future, this will create a global system of transmission of quantum information, and will remove restrictions for the quantum cryptography.
“Of course, for the restoration of confusion has to be paid – a million little entangled pairs of photons obtained a highly convoluted. But at the same level of correlation is restored to the primary, and while the data rate is somewhat reduced, we can get a stable connection at a much greater distance, “- concludes another author, Alexander Ulanov.
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