Hamburg 2009 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 13: Quanteninformation: Konzepte III

Q 13.5: Talk

Monday, March 2, 2009, 17:30–17:45, VMP 6 HS-D

Global Effects of Locally Noneffective Unitary Operations — •Hermann Kampermann¹, Sevag Gharibian^{1, 2}, and Dagmar Bruß¹ — ¹Theoretische Physik III, Universität Düsseldorf, Germany — ²Institute for Quantum Computing, University of Waterloo, Canada

We study the effect of locally noneffective unitary operations on bipartite quantum states, i.e. unitary operations applied to one party which leave the reduced density operator invariant. We investigate the distance between the bipartite state before and after such a local operation as an indicator for entanglement and non-locality [L.B. Fu, Europhys. Lett., vol. 75, 1 (2006)]. Closed formulae for the maximal distance induced by such operations (Fu-distance) are derived for pseudo pure quantum states, Werner states, and two-qubit states. The capabilities and limitations of the Fu-distance for entanglement detection is discussed as well as the connection to the CHSH inequality for specific classes of two-qubit states.