We introduce a multi-mode squeezing coefficient to characterize entanglement in N-partite continuous-variable systems. The coefficient relates to the squeezing of collective observables in the 2N-dimensional phase space and can be readily extracted from the covariance matrix. Simple extensions further permit to reveal entanglement within specific partitions of a multipartite system. Applications with nonlinear observables allow for the detection of non-Gaussian entanglement.
@article{arxiv.1702.08413,
title = {Entanglement and squeezing in continuous-variable systems},
author = {Manuel Gessner and Luca Pezzè and Augusto Smerzi},
journal= {arXiv preprint arXiv:1702.08413},
year = {2017}
}