title: Entangling the spatial properties of laser beams.
abstract: Position and momentum were the first pair of conjugate observables explicitly used to illustrate the intricacy of quantum mechanics. We have extended position and momentum entanglement to bright optical beams. Applications in optical metrology and interferometry require the continuous measurement of laser beams, with the accuracy fundamentally limited by the uncertainty principle. Techniques based on spatial entanglement of the beams could overcome this limit, and high-quality entanglement is required. We report a value of 0.51 for inseparability and 0.62 for the Einstein-Podolsky-Rosen criterion, both normalized to a classical limit of 1. These results are a conclusive optical demonstration of macroscopic position and momentum quantum entanglement and also confirm that the resources for spatial multimode protocols are available.
authors.affiliation: Australian Research Council Centre of Excellence for Quantum-Atom Optics, Australian National University, Canberra ACT 0200, Australia.
authors.forename: Katherine
authors.initials: K
authors.lastname: Wagner
authors.forename: Jiri
authors.initials: J
authors.lastname: Janousek
authors.forename: Vincent
authors.initials: V
authors.lastname: Delaubert
authors.forename: Hongxin
authors.initials: H
authors.lastname: Zou
authors.forename: Charles
authors.initials: C
authors.lastname: Harb
authors.forename: Nicolas
authors.initials: N
authors.lastname: Treps
authors.forename: Jean François
authors.initials: JF
authors.lastname: Morizur
authors.forename: Ping Koy
authors.initials: PK
authors.lastname: Lam
authors.forename: Hans A
authors.initials: HA
authors.lastname: Bachor