title: Induced coherence, vacuum fields, and complementarity in biphoton generation.
abstract: It is well established that spontaneous parametric down-conversion with induced coherence across two coupled interferometers results in high-visibility single-photon interference. We describe experiments in which additional photon channels are introduced such that "which-path" information is made possible and the fringe visibility in single-photon interference is reduced in accordance with basic notions of complementarity. However, these additional pathways result in nearly perfect visibility when photons are counted in coincidence. A simplified theoretical model accounts for these observations and attributes them directly to the vacuum fields at the different crystals.
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht Straß e 24-25, D-14476 Potsdam, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Heuer
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht Straß e 24-25, D-14476 Potsdam, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Menzel
authors.affiliation: Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA and Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA.
authors.forename: P W
authors.initials: PW
authors.lastname: Milonni