PPLN waveguide for quantum communication.

Authors :: Tanzilli, S.
Tittel, W.
De Riedmatten, H.
Zbinden, H.
Baldi, P.
DeMicheli, M.
Ostrowsky, D.B.
Gisin, N.
Source :: European Physical Journal D (EPJ D); Feb2002, Vol. 18 Issue 2, p155-160, 6p
Publication Year :: 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<superscript>-6</superscript>, roughly 4 orders of magnitude more than that obtained employing bulk crystals [#!Tanzilli01a!#]. 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. [ABSTRACT FROM AUTHOR]