title: Phonon-Mediated Nonclassical Interference in Diamond.
abstract: Quantum interference of single photons is a fundamental aspect of many photonic quantum processing and communication protocols. Interference requires that the multiple pathways through an interferometer be temporally indistinguishable to within the coherence time of the photon. In this Letter, we use a diamond quantum memory to demonstrate interference between quantum pathways, initially temporally separated by many multiples of the optical coherence time. The quantum memory can be viewed as a light-matter beam splitter, mapping a THz-bandwidth single photon to a variable superposition of the output optical mode and stored phononic mode. Because the memory acts both as a beam splitter and as a buffer, the relevant coherence time for interference is not that of the photon, but rather that of the memory. We use this mechanism to demonstrate nonclassical single-photon and two-photon interference between quantum pathways initially separated by several picoseconds, even though the duration of the photons themselves is just ∼250  fs.
authors: National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
authors: Duncan G
authors: DG
authors: England
authors: Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors: Kent A G
authors: KA
authors: Fisher
authors: Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors: Jean-Philippe W
authors: JP
authors: MacLean
authors: National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
authors: Philip J
authors: PJ
authors: Bustard
authors: National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
authors: Khabat
authors: K
authors: Heshami
authors: Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors: Kevin J
authors: KJ
authors: Resch
authors: National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.|Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
authors: Benjamin J
authors: BJ
authors: Sussman