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APS » Journals » Phys. Rev. Lett. » Volume 96 » Issue 17
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Phys. Rev. Lett. 96, 170502 (2006) [4 pages]

Nonlinear Entanglement Witnesses

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Otfried Gühne1 and Norbert Lütkenhaus2,3
1Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria
2Quantum Information Theory Group, Institut für Theoretische Physik I, and Max-Planck Research Group, Institute of Optics, Information and Photonics, Universität Erlangen-Nürnberg, Staudtstraße 7/B2, 91058 Erlangen, Germany
3Institute for Quantum Computing, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada

Received 9 January 2006; published 1 May 2006

Entanglement detection typically relies on linear inequalities for mean values of certain observables (entanglement witnesses), where violation indicates entanglement. We provide a general method to improve any of these inequalities for bipartite systems via nonlinear expressions. The nonlinearities are of different orders and can be directly measured in experiments, often without any extra effort.

© 2006 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.96.170502
DOI:
10.1103/PhysRevLett.96.170502
PACS:
03.67.Mn, 03.65.Ud
 
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