We report on energy-time and time-bin entangled photon-pair sources based on a periodically poled lithium niobate (PPLN) waveguide. Degenerate twin photons at 1314 nm wavelength are created by spontaneous parametric down-conversion and coupled into standard telecom fibers. Our PPLN waveguide features a very high conversion efficiency of about 10^(-6), roughly 4 orders of magnitude more than that obtained employing bulk crystals. Even if using low power laser diodes, this engenders a significant probability for creating two pairs at a time - an important advantage for some quantum communication protocols. We point out a simple means to characterize the pair creation probability in case of a pulsed pump. To investigate the quality of the entangled states, we perform photon-pair interference experiments, leading to visibilities of 97% for the case of energy-time entanglement and of 84% for the case of time-bin entanglement. Although the last figure must still be improved, these tests demonstrate the high potential of PPLN waveguide based sources to become a key element for future quantum communication schemes
@article{arxiv.quant-ph/0107125,
title = {PPLN Waveguide for Quantum Communication},
author = {S. Tanzilli and H. de Riedmatten and W. Tittel and H. Zbinden and P. Baldi and M. de Micheli and D. B. Ostrowsky and N. Gisin},
journal= {arXiv preprint arXiv:quant-ph/0107125},
year = {2009}
}
Comments
11 pages, 9 figures, submitted to the European Physical Journal D (special issue of the Quick conference)