Berlin 2005 – scientific programme
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TT: Tiefe Temperaturen
TT 13: Transport - Quantum Coherence and Quantum Information Systems
TT 13.5: Talk
Saturday, March 5, 2005, 09:45–10:00, TU H3027
Entanglement measures for multipartite qubit systems and beyond — •Andreas Osterloh1 and Jens Siewert2 — 1Institut für Theoretische Physik, Universität Hannover — 2DMFCI, Universitá di Catania, Catania, Italy
We propose an approach to construct entanglement measures for multipartite systems of qubits, which can be extended to an arbitrary number of half-integer spins. The essential step is the construction of an operator that we call comb in reference to the hairy ball theorem. These combs necessarily have to be antilinear operators. A particularily nice feature of this approach is that for qubits (or spin 1/2) the combs are automatically invariant under SL(2,.24em width.04em height1.46ex depth−.07ex −.30em C), which implies that the constructed measures are entanglement monotones by construction. The central idea provides a key to formulate (multipartite) entanglement measures for entanglement of arbitrary subsystems. In order to illustrate our appraoch, we construct operators for the N-tangle (N=3,…,6) Candidates for maximally entangled states are presented and their tangles are evaluated. An extension towards general half-integer spin is discussed.