Berlin 2014 – wissenschaftliches Programm

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SYQE: Symposium Quantum Correlations Beyond Entanglement

SYQE 2: Quantum Correlations Beyond Entanglement II

SYQE 2.3: Hauptvortrag

Dienstag, 18. März 2014, 17:30–18:00, Kinosaal

Comparing the private capacity and the locking capacity of a quantum channel — •Andreas Winter — Universitat Autonoma de Barcelona

Guha et al. [arXiv:1307.5368] have recently defined the locking capacity of a quantum channel as the largest rate of a uniformly distributed bit string, which Alice can share with Bob over the channel while an eavesdropper, Eve, who has access to the channel environment, can only gain negligible accessible information about the string. We show that this relaxation of the private capacity of a channel, can be much larger than the latter; in fact, if a sub- linear size key is shared between Alice and Bob, there are channels with zero private capacity but positive locking capacity. This gives a quantitative meaning to the information locking effect [DiVincenzo et al., PRL 92:067902, 2004], and answers an open question of Guha et al. The difference between private and locking capacity can also be related to non-zero discord, at least in some case.