Einstein-Podolsky-Rosen-like correlation on a coherent-state basis and inseparability of two-mode Gaussian states

摘要

The strange property of the Einstein-Podolsky-Rosen (EPR) correlation betweentwo remote physical systems is a primitive object on the study of quantumentanglement. In order to understand the entanglement in canonicalcontinuous-variable systems, a pair of the EPR-like uncertainties is anessential tool. Here, we consider a normalized pair of the EPR-likeuncertainties and introduce a state-overlap to a classically correlated mixtureof coherent states. The separable condition associated with this state-overlapdetermines the strength of the EPR-like correlation on a coherent-state basisin order that the state is entangled. We show that the coherent-state-basedcondition is capable of detecting the class of two-mode Gaussian entangledstates. We also present an experimental measurement scheme for estimation ofthe state-overlap by a heterodyne measurement and a photon detection with afeedforward operation.