Hannover 2010 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 11: Quantum Information: Concepts and Methods II
Q 11.1: Talk
Monday, March 8, 2010, 16:30–16:45, E 214
Practical methods for witnessing genuine multi-qubit entanglement in the vicinity of symmetric states — •Geza Toth1,2,3, Witlef Wieczorek4,5, Roland Krischek4,5, Nikolai Kiesel4,5,6, Patrick Michelberger4,5, and Harald Weinfurter4,5 — 1Theoretical Physics, The University of the Basque Country, E-48080 Bilbao, Spain — 2IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain — 3Research Institute for Solid State Physics and Optics, H-1525 Budapest, Hungary — 4Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany — 5Fakultät für Physik, Ludwig-Maximilians-Universität, D-80799 Garching, Germany — 6Institute for Quantum Optics and Quantum Information (IQOQI), A-1090 Vienna, Austria
We present general numerical methods to construct witness operators for entanglement detection and for the estimation of the fidelity. Our methods are applied to detecting entanglement in the vicinity of a six-qubit Dicke state with three excitations and also to further entangled symmetric states. All our witnesses are designed to keep the measurement effort small thus they are useful in many-qubit experiments. We present also general results on the efficient local decomposition of permutationally invariant operators, which makes it possible to measure projectors to symmetric states efficiently.