Baku, May 15 (AZERTAC). Teleportation is the extraordinary ability to transfer objects from one location to another without travelling through the intervening space. The idea is not that the physical object is teleported but the information that describes it. This can then be applied to a similar object in a new location which effectively takes on the new identity. Physicists have been teleporting photons since 1997 and the technique is now standard in optics laboratories all over the world. Teleportation turns out to be extremely useful. Because teleported information does not travel through the intervening space, it cannot be secretly accessed by an eavesdropper. In 2010, a Chinese team announced that it had teleported single photons over a distance of 16 kilometres. Now the same team says it has smashed this record. Juan Yin at the University of Science and Technology of China in Shanghai, and a bunch of mates say they have teleported entangled photons over a distance of 97 kilometres across a lake in China. Inevitably photons get lost and entanglement is destroyed in such a process. Imperfections in the optics and air turbulence account for some of these losses but the biggest problem is beam widening (they did the experiment at an altitude of about 4000 metres). Since the beam spreads out as it travels, many of the photons simply miss the target altogether. So the most important advance these guys have made is to develop a steering mechanism using a guide laser that keeps the beam precisely on target. As a result, they were able to teleport more than 1100 photons in 4 hours over a distance of 97 kilometres. That`s interesting because it`s the same channel attenuation that you`d have to cope with when beaming photons to a satellite with, say, 20 centimetre optics orbiting at about 500 kilometres. So these guys clearly have their eye on the possibility of satellite-based quantum cryptography which would provide ultra secure communications around the world.
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