title: Experimental violation of Bell's inequality in spatial-parity space.
abstract: We report the first experimental violation of Bell's inequality in the spatial domain using the Einstein-Podolsky-Rosen state. Two-photon states generated via optical spontaneous parametric down-conversion are shown to be entangled in the parity of their one-dimensional transverse spatial profile. Superpositions of Bell states are prepared by manipulation of the optical pump's transverse spatial parity-a classical parameter. The Bell-operator measurements are made possible by devising simple optical arrangements that perform rotations in the one-dimensional spatial-parity space of each photon of an entangled pair and projective measurements onto a basis of even-odd functions. A Bell-operator value of 2.389+/-0.016 is recorded, a violation of the inequality by more than 24 standard deviations.
authors.affiliation: Quantum Imaging Laboratory, Departments of Electrical and Computer Engineering and Physics, Boston University, Boston, Massachusetts 02215-2421, USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Yarnall
authors.forename: Ayman F
authors.initials: AF
authors.lastname: Abouraddy
authors.forename: Bahaa E A
authors.initials: BE
authors.lastname: Saleh
authors.forename: Malvin C
authors.initials: MC
authors.lastname: Teich