Complete bi-partite CV entanglement characterization via coveriance matrix measurement

Abstract

We report the first complete experimental reconstruction of the covariance matrix (CM) relative to a bi-partite continuous variable (CV) entangled state outing a non degenerate optical parametric oscillator (OPO) below threshold. The covariance matrix CM has been reconstructed following the method reported in V. D'Auria et al., J. Opt. B 7, S750 (2005). The two entangled beams (signal (a) and idler (b)) are produced by a by a continuous wave (CW) optical parametric oscillator (OPO) via type-II (same frequency but with orthogonal polarizations), phase matching and working below threshold. Our experimental setup makes use of a single homodyne detector and of a compact source of entangled beams. The quadratures values and other relevant quantities are reconstructed by quantum tomography, without making any a priori assumption on the state under evalutation.