On the Cover of "Nature" (22 May 2003)
22. May 2003
"Experimental purification of arbitrary unknown states"
by Jian-Wei Pan, Sara Gasparoni, Rupert Ursin, Gregor Weihs and Anton Zeilinger.
Distribution of entangled states between distant locations is essential for quantum communication over large distances. But owing to unavoidable decoherence in the quantum communication channel, the quality of entangled states generally decreases with the channel length. Entanglement purification is a way to extract a subset of states of high entanglement and high purity from a large set of less entangled states - and is thus needed to overcome decoherence.