title: Identifying entanglement using quantum ghost interference and imaging.
abstract: We report a quantum interference and imaging experiment which allows identifying the entanglement in momentum and position variables of a two-photon system. The measurements show indeed that the uncertainties in the sum of momenta and in the difference of positions of the entangled two-photon satisfy both EPR inequalities Delta(k(1)+k(2))<min((Delta k(1),Delta k(2)) and Delta(x(1)-x(2))<min((Delta x(1),Delta x(2)). These two inequalities, together, represent a nonclassicality condition. Our measurements provide a direct way to distinguish between quantum entanglement and classical correlation in continuous variables for systems of pairs of photons.
authors.affiliation: Department of Physics, University of Maryland, Baltimore County, Baltimore, Maryland, 21250, USA. dmilena1@umbc.edu
authors.forename: Milena
authors.initials: M
authors.lastname: D'Angelo
authors.forename: Yoon-Ho
authors.initials: YH
authors.lastname: Kim
authors.forename: Sergei P
authors.initials: SP
authors.lastname: Kulik
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Shih