title: Efficient photon triplet generation in integrated nanophotonic waveguides.
abstract: Generation of entangled photons in nonlinear media constitutes a basic building block of modern photonic quantum technology. Current optical materials are severely limited in their ability to produce three or more entangled photons in a single event due to weak nonlinearities and challenges achieving phase-matching. We use integrated nanophotonics to enhance nonlinear interactions and develop protocols to design multimode waveguides that enable sustained phase-matching for third-order spontaneous parametric down-conversion (TOSPDC). We predict a generation efficiency of 0.13 triplets/s/mW of pump power in TiO2-based integrated waveguides, an order of magnitude higher than previous theoretical and experimental demonstrations. We experimentally verify our device design methods in TiO2waveguides using third-harmonic generation (THG), the reverse process of TOSPDC that is subject to the same phase-matching constraints. We finally discuss the effect of finite detector bandwidth and photon losses on the energy-time coherence properties of the expected TOSPDC source.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Moebius
authors.forename: Felipe
authors.initials: F
authors.lastname: Herrera
authors.forename: Sarah
authors.initials: S
authors.lastname: Griesse-Nascimento
authors.forename: Orad
authors.initials: O
authors.lastname: Reshef
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Evans
authors.forename: Gian Giacomo
authors.initials: GG
authors.lastname: Guerreschi
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
authors.forename: Eric
authors.initials: E
authors.lastname: Mazur