Hannover 2010 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 11: Quantum Information: Concepts and Methods II
Q 11.5: Vortrag
Montag, 8. März 2010, 17:30–17:45, E 214
Estimates for the three-tangle from incomplete information — •Andreas Osterloh1 and Philipp Hyllus2 — 1FB Physik, Universität Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg, Germany. — 2BEC-INFM, Dipartimento di Fisica, Università di Trento, Via Sommarive 14, I-38050 Povo, Italy.
We investigate the lower bound obtained from experimental data of a quantum state ρ, as proposed independently by Gühne et al. and Eisert et al. [1] and apply it to mixed states of three qubits. The measure we consider is the convex-roof extension of the three-tangle [2]. Our findings highlight an intimate relation to lower bounds obtained recently from so-called characteristic curves of a given entanglement measure [3]. For an unstructured admixture to a GHZ state the non-vanishing lower bound is obtained if the GHZ-fidelity of the produced states is larger than 3/4, which reproduces the result obtained from witnesses. We apply the bounds to estimate the three-tangle present in recently performed experiments aimed at producing a three-qubit GHZ state.
[1] O. Gühne, M. Reimpell, and R.F. Werner, PRL 98, 110502 (2007); J. Eisert, F.G.S.L. Brandão, and K. Audenaert, NJP 9, 46 (2007).
[2] V. Coffman, J. Kundu, and W.K. Wootters, PRA 61, 052306 (2000).
[3] A. Osterloh, J. Siewert, and A. Uhlmann, Phys. Rev. A 77, 032310 (2008).