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arXiv · 2103.15730

Entanglement quantification in atomic ensembles

Matteo Fadel·Ayaka Usui·Marcus Huber·Nicolai Friis·Giuseppe Vitagliano
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Abstract

Entanglement measures quantify nonclassical correlations present in a quantum system, but can be extremely difficult to calculate, even more so, when information on its state is limited. Here, we consider broad families of entanglement criteria that are based on variances of arbitrary operators and analytically derive the lower bounds these criteria provide for two relevant entanglement measures: the best separable approximation (BSA) and the generalized robustness (GR). This yields a practical method for quantifying entanglement in realistic experimental situations, in particular, when only few measurements of simple observables are available. As a concrete application of this method, we quantify bipartite and multipartite entanglement in spin-squeezed Bose-Einstein condensates of $\sim 500$ atoms, by lower bounding the BSA and the GR only from measurements of first and second moments of the collective spin operator.

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Matteo Fadel, Ayaka Usui, Marcus Huber, Nicolai Friis, Giuseppe Vitagliano. 2021-03-29. Entanglement quantification in atomic ensembles. https://doi.org/10.1103/physrevlett.127.010401

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