A big step closer to teleportationJoana Rodeiro ▼ |
Scientists in China have succeeded in teleporting information between photons further than ever before. They transported quantum information over a free space distance of 16 km, much further than the few hundred meters previously achieved, which brings us closer to transmitting information over long distances without the need for a traditional signal.
Quantum teleportation is not the same as the teleportation most of us know from science fiction, where an object or a person in one place is "beamed up" to another place where a perfect copy is replicated. In quantum teleportation two photons are entangled in such a way that when the quantum state of one is changed the state of the other also changes, as if the two were still connected. This enables quantum information to be teleported if one of the photons is sent some distance away.
In previous experiments the photons were confined to fiber channels a few hundred meters long to ensure their state remained unchanged, but in the new experiments pairs of photons were entangled and then the higher-energy photon of the pair was sent through a free space channel 16 km long. The researchers found that even at that distance the photon at the receiving end still responded to changes in state of the photon remaining behind. The average fidelity of the teleportation achieved was 89 percent.
The distance of 16 km is greater than the effective aerosphere thickness of 5-10 km, so the group's success could pave the way for experiments between a ground station and a satellite, or two ground stations with a satellite acting as a relay. This means quantum communication applications could be possible on a global scale in the near future.
The public free space channel was at ground level and spanned the 16 km distance between the teleportation site in Beijing and the receiver site at Huailai in Hebei province. Entangled photon pairs were generated at the teleportation site using a semiconductor, a blue laser beam, and a crystal. The pairs of photons were entangled in the spatial modes of photon 1 and polarization modes of photon 2. The research team designed two types of telescopes to serve as optical transmitting and receiving antennas.
This experiments confirm the feasibility of space-based quantum teleportation, and represent a giant leap forward in the development of quantum communication applications. ■