title: Quantifying the momentum correlation between two light beams by detecting one.
abstract: We report a measurement of the transverse momentum correlation between two photons by detecting only one of them. Our method uses two identical sources in an arrangement in which the phenomenon of induced coherence without induced emission is observed. In this way, we produce an interference pattern in the superposition of one beam from each source. We quantify the transverse momentum correlation by analyzing the visibility of this pattern. Our approach might be useful for the characterization of correlated photon pair sources and may lead to an experimental measure of continuous variable entanglement, which relies on the detection of only one of two entangled particles.
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Vienna A-1090, Austria; anton.zeilinger@univie.ac.at armin.hochrainer@univie.ac.at.|Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Vienna A-1090, Austria.
authors.forename: Armin
authors.initials: A
authors.lastname: Hochrainer
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Vienna A-1090, Austria.|Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Vienna A-1090, Austria.
authors.forename: Mayukh
authors.initials: M
authors.lastname: Lahiri
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Vienna A-1090, Austria.|Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Vienna A-1090, Austria.
authors.forename: Radek
authors.initials: R
authors.lastname: Lapkiewicz
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Vienna A-1090, Austria.|Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Vienna A-1090, Austria.
authors.forename: Gabriela Barreto
authors.initials: GB
authors.lastname: Lemos
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Vienna A-1090, Austria; anton.zeilinger@univie.ac.at armin.hochrainer@univie.ac.at.|Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Vienna A-1090, Austria.
authors.forename: Anton
authors.initials: A
authors.lastname: Zeilinger
keywords: complementarity principle; photon indistinguishability; photonic spatial modes; quantum correlations; single-photon interference