Heidelberg 2015 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 26: Quantum Information: Concepts and Methods IV

Q 26.6: Talk

Tuesday, March 24, 2015, 15:45–16:00, K/HS1

Generalized spin squeezing in the vicinity of Dicke states — •Giuseppe Vitagliano¹, Iagoba Apellaniz¹, Iñigo Egusquiza¹, Geza Toth^1,2,3, Bernd Lucke⁴, Jan Peise⁴, and Carsten Klempt⁴ — ¹Theoretical Physics, University of the Basque Country UPV/EHU, E-48080 Bilbao, Spain — ²IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain — ³Wigner Research Centre for Physics, H-1525 Budapest, Hungary — ⁴Institut fur Quantenoptik, Leibniz Universitat Hannover, Welfengarten 1, D-30167 Hannover, Germany

We study the problem of detecting entanglement and its depth in systems composed of very many particles. We derive entanglement criteria based only on few easy measurable quantities such as the mean values and variances of collective spin components. In particular we present what we call a generalized spin squeezing parameter, that can be used to detect a class of states wider than the spin squeezed states as defined in [A. Sorensen et al., Nature 409, 63 (2001)]. Moreover we present a criterion to estimate the entanglement depth that outperforms previous well-known criteria. It has been used in a recent experiment [B. Lucke et al., PRL 112, 155304 (Editor's suggestion)] to prove that the produced Dicke-like state had an entanglement depth of at least 28 particles.