title: Optical π phase shift created with a single-photon pulse.
abstract: A deterministic photon-photon quantum logic gate is a long-standing goal. Building such a gate becomes possible if a light pulse containing only one photon imprints a phase shift of π onto another light field. We experimentally demonstrate the generation of such a π phase shift with a single-photon pulse. A first light pulse containing less than one photon on average is stored in an atomic gas. Rydberg blockade combined with electromagnetically induced transparency creates a phase shift for a second light pulse, which propagates through the medium. We measure the π phase shift of the second pulse when we postselect the data upon the detection of a retrieved photon from the first pulse. This demonstrates a crucial step toward a photon-photon gate and offers a variety of applications in the field of quantum information processing.
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Tiarks
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Schmidt
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rempe
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Dürr
mesh_terms: D008027:Light; D055095:Optics and Photonics; D017785:Photons; D011789:Quantum Theory
keywords: Quantum photonics; Rydberg atoms