title: Entanglement can completely defeat quantum noise.
abstract: We describe two quantum channels that individually cannot send any classical information without some chance of decoding error. But together a single use of each channel can send quantum information perfectly reliably. This proves that the zero-error classical capacity exhibits superactivation, the extreme form of the superadditivity phenomenon in which entangled inputs allow communication over zero-capacity channels. But our result is stronger still, as it even allows zero-error quantum communication when the two channels are combined. Thus our result shows a new remarkable way in which entanglement across two systems can be used to resist noise, in this case perfectly. We also show a new form of superactivation by entanglement shared between sender and receiver.
authors.affiliation: Department of Mathematics & Statistics, U. of Guelph, Guelph, Ontario, Canada.
authors.forename: Jianxin
authors.initials: J
authors.lastname: Chen
authors.forename: Toby S
authors.initials: TS
authors.lastname: Cubitt
authors.forename: Aram W
authors.initials: AW
authors.lastname: Harrow
authors.forename: Graeme
authors.initials: G
authors.lastname: Smith