title: Nonlinear quantum optics in a waveguide: distinct single photons strongly interacting at the single atom level.
abstract: We propose a waveguide-QED system where two single photons of distinct frequency or polarization interact strongly. The system consists of a single ladder-type three level atom coupled to a waveguide. When both optical transitions are coupled strongly to the waveguide's mode, we show that a control photon tuned to the upper transition induces a π phase shift and tunneling of a probe photon tuned to the otherwise reflective lower transition. Furthermore, the system exhibits single photon scattering by a classical control beam. Waveguide-QED schemes could be an alternative to high quality cavities or dense atomic ensembles in quantum information processing.
authors.affiliation: Nanoscale Science and Engineering Center, 3112 Etcheverry Hall, University of California, Berkeley California 94720, USA.
authors.forename: Pavel
authors.initials: P
authors.lastname: Kolchin
authors.forename: Rupert F
authors.initials: RF
authors.lastname: Oulton
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhang