Sending signals through fibre optic cable is reliable and fast, but because of internal absorption and other effects, they will lose photons -- which is a problem when the number of photons being sent is small. This is of particular concern in quantum networks, which typically involve a small number of entangled photons. Direct transmission through free space (vacuum or air) experiences less photon loss, but it's very difficult to align a distant receiver perfectly with the transmitter so that photons arrive at their destination.
A group in China has made significant progress toward solving that problem, via a high accuracy pointing and tracking system. Using this method, Juan Yin and colleagues performed quantum teleportation (copying of a quantum state) using multiple entangled photons through open air between two stations 97 kilometres apart across a lake. Additionally, they demonstrated entanglement between two receivers separated by 101.8km, transmitted by a station on an island roughly halfway between them.
By: Matthew Francis, Edited by: Ian Steadman
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via Wired.co.uk
http://www.wired.co.uk/news/archive/2012-08/10/quantum-teleportation
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