Efficient single-spatial-mode periodically-poled KTiOPO_4 waveguide source for high-dimensional entanglement-based quantum key distribution

• DOI: 10.1364/oe.20.026868
• Publication Date: 2012-11-14T15:48:56Z
• Authors: Tian Zhong; Franco N. C. Wong; Alessandro Restelli; Joshua C. Bienfang
• Keywords: Titanium; Quantum Physics; Photons; FOS: Physical sciences; Signal Processing, Computer-Assisted; Equipment Design; 7. Clean energy; 01 natural sciences; Phosphates; 0103 physical sciences; Telecommunications; Humans; Scattering, Radiation; Computer Simulation; Quantum Physics (quant-ph)

We demonstrate generation of high-purity photon pairs at 1560 nm in a single spatial mode from a periodically-poled KTiOPO_4 (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.