title: Efficient single-spatial-mode periodically-poled KTiOPO4 waveguide source for high-dimensional entanglement-based quantum key distribution.
abstract: We demonstrate generation of high-purity photon pairs at 1560 nm in a single spatial mode from a periodically-poled KTiOPO4 (PPKTP) waveguide. With nearly lossless spectral filtering, the PPKTP waveguide source shows approximately 80 % single-mode fiber coupling efficiency and is well suited for high-dimensional time-energy entanglement-based quantum key distribution. Using high-count-rate self-differencing InGaAs single-photon avalanche photodiodes configured with either square or sinusoidal gating, we achieve > 1 Mbit/s raw key generation with 3 bits-per-photon encoding, and, to the best of our knowledge, the highest reported Franson quantum-interference visibility of 98.2 % without subtraction of accidental coincidences.
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. tzhong@mit.edu
authors.forename: Tian
authors.initials: T
authors.lastname: Zhong
authors.forename: Franco N C
authors.initials: FN
authors.lastname: Wong
authors.forename: Alessandro
authors.initials: A
authors.lastname: Restelli
authors.forename: Joshua C
authors.initials: JC
authors.lastname: Bienfang
mesh_terms: D003198:Computer Simulation; D004867:Equipment Design; D006801:Humans; D010710:Phosphates / Q000737:chemistry*; D017785:Photons; D012542:Scattering, Radiation; D012815:Signal Processing, Computer-Assisted; D013685:Telecommunications / Q000295:instrumentation*; D014025:Titanium / Q000737:chemistry*
chemical_list: D010710:Phosphates; C064806:potassium titanylphosphate; D014025:Titanium