Berlin 2014 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 50: Quantum information: Concepts and methods III
Q 50.4: Talk
Thursday, March 20, 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 [1] 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 [2], which outperform traditional methods for detecting entanglement in spin ensembles (like the criterion of Ref. [3]). 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.
[1] GV, P. Hyllus, I.L. Egusquiza, and G. Tóth, PRL 107, 240502
[2] GV, I. Apellaniz, I.L. Egusquiza, and G. Tóth, arXiv:1310.2269
[3] A. Sørensen, L.-M. Duan, J.I. Cirac, P. Zoller, Nature 409, 63 (2001).