%0 Journal Article %J Optics Express %D 2016 %T Efficient photon triplet generation in integrated nanophotonic waveguides %A M. Gerhard Moebius %A F. Herrera %A S. Griesse-Nascimento %A O. Reshef %A C. C. Evans %A G. G. Guerreschi %A A. n. Aspuru-Guzik %A Mazur, E. %X 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 TiO2 waveguides 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. %B Optics Express %V 24 %P 9932–9954 %G eng %U /files/mazur/files/rep_767.pdf %R 10.1364/OE.24.009932