Eur. Phys. J. D 18, 155-160 (2002)
https://doi.org/10.1140/epjd/e20020019

PPLN waveguide for quantum communication

¹ Laboratoire de Physique de la Matière Condensée (UMR 6622 du CNRS) , Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France
² Group of Applied Physics, Université de Genève, 20 rue de l'École-de-Médecine, 1211 Geneva 4, Switzerland

Corresponding author: ^a tanzilli@unice.fr

Received: 13 July 2001
Published online: 15 February 2002

Abstract

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 1 314 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 [1]. 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.