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Q: Fachverband Quantenoptik und Photonik

Q 34: Quanteninformation: Konzepte IV

Q 34.5: Vortrag

Mittwoch, 4. März 2009, 15:00–15:15, VMP 6 HS-D

Characterizing entanglement with geometric entanglement witnesses — •Philipp Krammer — Fakultät für Physik, Universität Wien, A-1090 Vienna, Austria — Institut für Theoretische Physik III, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany

A challenge in quantum information theory is the detection of entangled states on a finite dimensional Hilbert space. Useful tools for this purpose are entanglement witnesses; they provide a geometrically intuitive method to detect entanglement.

We show how to detect entangled, bound entangled, and separable bipartite quantum states of arbitrary dimension and mixedness using geometric entanglement witnesses. These witnesses are constructed using properties of the Hilbert-Schmidt geometry and can be shifted along parameterized lines. The involved conditions are simplified using Bloch decompositions of operators and states. As an example we determine the three different types of states for a family of two-qutrit states that is part of the ``magic simplex'', i.e. the set of Bell-state mixtures of arbitrary dimension.