We present experimental results on quantum frequency down-conversion of indistinguishable single photons emitted by an InAs/GaAs quantum dot at 904 nm to the telecom C-band at 1557 nm. Hong-Ou-Mandel (HOM)interference measurements are shown prior to, and after the down-conversion step. We perform Monte Carlo simulations of the HOM experiments taking into account the time delays of the different interferometers used and the signal-to-background ratio and further estimate the impact of spectral diffusion on the degree of indistinguishability. By that we conclude that the down-conversion step does not introduce any loss of HOM interference visibility. A noise-free conversion-process along with a high conversion-efficiency (> 30%)emphasize that our scheme is a promising candidate for an efficient source of indistinguishable single photons at telecom wavelengths.
Publication: Low-noise quantum frequency down-conversion of indistinguishable photons
Benjamin Kambs, Jan Kettler, Matthias Bock , Jonas Nils Becker, Carsten Arend, Andreas Lenhard, Simone Luca Portalupi, Michael Jetter, Peter Michler, Christoph Becher 
Opt. Express 24, 22250 (2016)
Contact person: Jonas Weber