München 2004 – scientific programme

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Q: Quantenoptik und Photonik

Q 52: Postdeadline

Q 52.11: Talk

Thursday, March 25, 2004, 21:40–21:50, HS 225

Nonlocal resources in the presence of Superselection Rules — •Norbert Schuch, Frank Verstraete, and Ignacio Cirac — Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str.1, D-85748 Garching

Superselection rules severely alter the possible operations that can be implemented on a distributed quantum system. Whereas the restriction to local operations imposed by a bipartite setting gives rise to the notion of entanglement as a nonlocal resource, the superselection rule associated with particle number conservation leads to a new resource, the superselection induced variance of local particle number. We show that, in the case of pure quantum states, one can quantify the nonlocal properties by only two additive measures, and that all states with the same measures can be asymptotically interconverted into each other by local operations and classical communication. Furthermore, we discuss how these concepts can be extended to mixed state entanglement and how the new resource can be used to overcome the restrictions imposed by the superselection rule.