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SYQI: Symposium Quanteninformationsverarbeitung

SYQI 2: Quanteninformationsverarbeitung II

SYQI 2.5: Talk

Monday, March 15, 1999, 15:15–15:30, PH1

Lower Bounds for Attainable Fidelities in Entanglement Purification — •Geza Giedke¹, Hans J. Briegel^1,2, Ignacio Cirac¹, and Peter Zoller¹ — ¹Institut für Theoretische Physik, Universität Innsbruck, A–6020 Innsbruck — ²Sektion Physik, Ludwig-Maximilians-Universität, Theresienstr. 37, D–80333 München

We derive lower bounds for the attainable fidelity of standard entanglement purification protocols when local operations and measurements are subjected to errors. We introduce an error parameter which measures the distance between the ideal completely positive map describing a purification step and the one in the presence of errors. We derive non–linear maps for a lower bound of the fidelity at each purification step in terms of this parameter. From these we obtain expressions for an error threshold and for lower bounds for the asymptotically attainable fidelity.