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Q: Quantenoptik und Photonik

Q 75: Poster Quanteninformation

Q 75.7: Poster

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

Entanglement witnesses and the loophole-problem — •P. Skwara, H. Kampermann, and D. Bruß — Heinrich-Heine-Universität Düsseldorf, Institut für theoretische Physik III

In analogy to loopholes in Bell-experiments we consider possible loopholes in experiments to measure entanglement witnesses, with special emphasis on the detector-efficiency-loophole[1]. We derive bounds for the detector-efficiency, which guarantees that a negative expectation value of the witness is due to entanglement, rather than to erroneous detectors. The decomposition of two-qubit witnesses into local measurements[2] is optimized with respect to the detector-efficiency. A generalization of this method to the case of two qudits is presented.

[1] J.-Å. Larsson, Phys. Rev. A 57, 3304, 1998

[2] O. Gühne, P. Hyllus, D. Bruß, M. Lewenstein, C. Macchiavello, A. Sanpera, Phys. Rev. A 66, 62305, 2002