Berlin 2014 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 50: Quantum information: Concepts and methods III
Q 50.4: Vortrag
Donnerstag, 20. März 2014, 17:15–17:30, Kinosaal
Generalized squeezing inequalities, entanglement and its depth — Giuseppe Vitagliano1, Zoltan Zimboras1, and •Geza Toth1,2,3 — 1Department of Theoretical Physics, University of the Basque Country UPV/EHU, P.O. Box 644, E-48080 Bilbao, Spain — 2IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain — 3Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary
We present a general method to derive sets of SU(d) squeezing inequalities for d-level particle systems. In  we presented a set of necessary separability criteria based on the first and the “modified” second moments of collective operators. Considering the total spin components as collective operators, these conditions yield the so-called generalized spin squeezing inequalities , which outperform traditional methods for detecting entanglement in spin ensembles (like the criterion of Ref. ). Here we present similar entanglement conditions based on the first and modified second moments of the collective SU(d)-generators. From these we define a parameter that is suitable to detect entangled states that might be useful for quantum metrology and even states that are biseparable with respect to all possible bipartitions. We also present a criterion for detecting the entanglement depth, i.e., whether the state is k-producible or not.
 GV, P. Hyllus, I.L. Egusquiza, and G. Tóth, PRL 107, 240502
 GV, I. Apellaniz, I.L. Egusquiza, and G. Tóth, arXiv:1310.2269
 A. Sørensen, L.-M. Duan, J.I. Cirac, P. Zoller, Nature 409, 63 (2001).