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Q: Quantenoptik und Photonik

Q 76: Poster Quantenkommunikation

Q 76.1: Poster

Thursday, March 16, 2006, 16:30–18:30, Labsaal

Asymptotic correctability of Bell-diagonal quantum states and maximum tolerable bit error rates — •Kedar Ranade and Gernot Alber — Institut für Angewandte Physik, TU Darmstadt, 64289 Darmstadt

The general conditions are discussed which quantum state purification protocols have to fulfill in order to be capable of purifying Bell-diagonal qubit-pair states, provided they consist of steps that map Bell-diagonal states to Bell-diagonal states and they finally apply a suitably chosen Calderbank-Shor-Steane code to the outcome of such steps. As a main result a necessary and a sufficient condition on asymptotic correctability are presented, which relate this problem to the magnitude of a characteristic exponent governing the relation between bit and phase errors under the purification steps. These conditions allow a straightforward determination of maximum tolerable bit error rates of quantum key distribution protocols whose security analysis can be reduced to the purification of Bell-diagonal states.