A successful test in passing information from light into matter – using the teleportation of the quantum state of a photon via optical fiber cable to a receiving crystal located over 25 km (15 mi) away – has been claimed by physicists at the University of Geneva. This test shattered the same team’s previous record and may herald the development of greater, long-distance teleportation techniques and qubit communications and computing capabilities.
The experiment involved generating a quantum entanglement of two photons via a laser, then sending one of those entangled photons down an optical fiber whilst simultaneously sending the other to a crystal (composed of yttrium orthosilicate), where it was stored. A third photon was then sent to hit the first photon in the optical fiber, obliterating both itself and the first photon.
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The researchers then used a device to measure the results of this collision and discovered that the quantum state information contained in the third photon was not actually destroyed, but had made its way into the crystal where the second entangled photon was contained.
In other words, the information contained in the third photon was transferred to the crystal, verifying that the quantum state of a photon can be preserved without the two photons needing to come into direct contact with each other. As such, the crystal acts as a memory store for the quantum information contained on the transmitted photon.
"The quantum state of the two elements of light, these two entangled photons which are like two Siamese twins, is a channel that empowers the teleportation from light into matter," said Dr. Felix Bussieres, senior researcher and lead author of the work.
This work is not the first time that the teleportation of quantum state information has been transmitted over a distance – the University of Geneva team itself conducted a similar successful experiment in 2003 over a distance of 6 km (3.7 mile), and scientists at TU Delft teleported qubit information between diamonds across the width of a room in another experiment. However, this long-range experiment not only exceeds the team's previous test distances, it is also the first successful mapping of energy–time entangled photons onto a quantum memory.
As a result of this research, possibilities may be opened up in the long-distance transmission of qubit information, which may lead to advances in the fields of quantum cryptography, quantum cloud computing, and of course, quantum teleportation.
The team's study is published in the journal Nature Photonics.
Source: University of Geneva