Quantum teleportation successful over 10 miles

Monday, May 24, 2010, 14:55 by Tech Correspondent

Scientists from the University of Science and Technology, China and from Tsinghua University in Beijing have conducted successful experiments in teleporting information between photons in a distance longer than ever before.

They were successful enough in transporting quantum information over a free space distance of 10 miles, much longer than the few hundred meters previously achieved. This brings mankind closer to transmitting information over long distances without the need for a traditional signal. In quantum teleportation, two photons or ions are entangled in such a way that when the quantum state of one is changed, the state of other also changes as if the two were connected.

According to a paper published in Nature Photonics, the experiment was such that pairs of photons were entangled and then the higher-energy photon of the pair was sent through a free space channel 16 km long. It was found that even at this distance the photon at the receiving end still responded to changes. This enables quantum information to be teleported if one of the photons is sent at a long distance. The distance of 16 km is greater than the effective aerosphere thickness 5-10 km. The experiments were conducted between a ground station and a satellite and or two ground stations with a satellite acting as a relay.

The public free space channel was at ground level and spanned the 16 km distance between Badaling in Beijing and the receiver site at Huailai in Hebei province. The pairs of photons were entangled in the spatial modes of photon 1 and polarization modes of photon 2. These were generated at the teleportation site using a semiconductor, a blue laser beam, and a crystal of beta-barium borate. These experiments represent a step into development of quantum communications applications and is seen as opening the path forward for many such experiments in this domain.

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