Düsseldorf 2007 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 38: Quanteninformation (Konzepte I)

Q 38.3: Talk

Wednesday, March 21, 2007, 12:30–12:45, 5L

Entanglement in three-qubit mixtures from GHZ and W states — Robert Lohmayer¹, Andreas Osterloh², •Jens Siewert¹, and Armin Uhlmann³ — ¹Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg — ²Institut für Theoretische Physik, Universität Hannover, 30167 Hannover — ³Institut für Theoretische Physik, Universität Leipzig, 04009 Leipzig

We provide a complete analysis of mixed three-qubit states composed of a GHZ state and a W state orthogonal to the former. We present optimal decompositions and convex roofs for the three-tangle. These results highlight intriguing differences compared to the properties of two-qubit mixed states, and may serve as a quantitative reference for future studies of entanglement in multipartite mixed states.
From our studies we derive an analytical method to decide whether or not an arbitrary rank-2 state of three qubits has vanishing three-tangle. This result can be generalized for N-tangles of rank-2 N-qubit states (N≥ 3).
Reference:
R. Lohmayer, A. Osterloh, J. Siewert, A. Uhlmann, e-print quant-ph/0606071 (2006), accepted for publication in Physical Review Letters.