Physicists Achieve Quantum Teleportation of Photon Over 25 Kilometers
by Lisa Winter
Photo credit: University of Geneva
For the first time, a team of physicists have successfully teleported a quantum state of a photon to a crystal over 25 kilometers away through a fiber optic cable. This effectively showed that the photon’s quantum state, not its composition, is important to the teleportation process. The team was led by Nicolas Gisin of the University of Geneva and the results were published in the journal Nature Photonics. With this new paper, Gisin’s team has successfully squashed the previous record they set a decade ago by teleporting a quantum state of a proton 6 kilometers.
The quantum state of the photon is able to preserve information under extreme conditions, including the difference between traveling as light or becoming stored in the crystal like matter. The photon’s state acts as information that can be teleported along great distances using the optical fiber, and can be stored within the crystal. This was achieved due to a phenomenon in quantum mechanics known as entanglement, where two particles have a correlation, despite the fact that they aren’t touching and transmitting information to one another.
To test this and ensure what they were observing was actually happening, one photon was stored in a crystal while the other was sent along optical fiber, over a distance of 25 kilometers. The photon that was sent along the optical fiber collides with a third photon, which was assumed to destroy them both. However, the information from the first photon was transferred to the third photon in the collision, like the transfer of energy when one billiard ball hits another. The information from the third photon came back to the crystal where it could be measured to ensure the information was preserved between the first and the second.
The photon did not physically “teleport” as we are used to hearing about in science fiction, where someone’s body can moved from place to place in a matter of seconds. Instead, the information contained on the now-distant photon can be inferred based on what is seen with the information in the photon in the crystal. By knowing one, you already know the other. However, what the information actually is can’t be known until it is examined.
Félix Bussières of Gisin’s team explained in a press release that it appears “that 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.” Regardless if the information was in crystal or light, there wasn’t a change to the information itself. This could very well mean that the quantum state, not physical state, rules in quantum physics.
Quantum entanglement is the basis for theoretical quantum computing and quantum communication, though it will be a very long time before these results will have real-world implications. The achievements of Gisin’s lab could also improve how quantum entanglement interactions are measured.