title: Entangled optical vortex links.
abstract: Optical vortices are lines of phase singularity which percolate through all optical fields. We report the entanglement of linked optical vortex loops in the light produced by spontaneous parametric down-conversion. As measured by using a Bell inequality, this entanglement between topological features extends over macroscopic and finite volumes. The entanglement of photons in complex three-dimensional topological states suggests the possibility of entanglement of similar features in other quantum systems describable by complex scalar functions, such as superconductors, superfluids, and Bose-Einstein condensates.
authors.affiliation: School of Physics and Astronomy, SUPA, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Romero
authors.forename: J
authors.initials: J
authors.lastname: Leach
authors.forename: B
authors.initials: B
authors.lastname: Jack
authors.forename: M R
authors.initials: MR
authors.lastname: Dennis
authors.forename: S
authors.initials: S
authors.lastname: Franke-Arnold
authors.forename: S M
authors.initials: SM
authors.lastname: Barnett
authors.forename: M J
authors.initials: MJ
authors.lastname: Padgett