Full characterization of Gaussian bipartite entangled states by a single homodyne detector

Abstract

We present the full experimental reconstruction of Gaussian entangled states generated by a type--II optical parametric oscillator (OPO) below threshold. Our scheme provides the entire covariance matrix using a single homodyne detector and allows for the complete characterization of bipartite Gaussian states, including the evaluation of purity, entanglement and nonclassical photon correlations, without a priori assumptions on the state under investigation. Our results show that single homodyne schemes are convenient and robust setups for the full characterization of OPO signals and represent a tool for quantum technology based on continuous variable entanglement.

4 pages, 3 figures, slightly longer version of published PRL

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• A possible experimental check of the uncertainty relations by means of homodyne measuring photon quadrature
• Complete State Reconstruction of a Two-Mode Gaussian State via Local Operations and Classical Communication