title: Observation of entanglement between two light beams spanning an octave in optical frequency.
abstract: We have experimentally demonstrated how two beams of light separated by an octave in frequency can become entangled after their interaction in a chi;{(2)} nonlinear medium. The entangler was a nonlinear optical resonator that was strongly driven by coherent light at the fundamental and second-harmonic wavelengths. An interconversion between the fields created quantum correlations in the amplitude and phase quadratures, which were measured by two independent homodyne detectors. Analysis of the resulting correlation matrix revealed a wave function inseparability of 0.74(1)<1, thereby satisfying the criterion of entanglement.
authors.affiliation: Quantum Optics Group, Department of Physics, Faculty of Science, The Australian National University, ACT 0200, Australia.
authors.forename: Nicolai B
authors.initials: NB
authors.lastname: Grosse
authors.forename: Syed
authors.initials: S
authors.lastname: Assad
authors.forename: Moritz
authors.initials: M
authors.lastname: Mehmet
authors.forename: Roman
authors.initials: R
authors.lastname: Schnabel
authors.forename: Thomas
authors.initials: T
authors.lastname: Symul
authors.forename: Ping Koy
authors.initials: PK
authors.lastname: Lam