Development of a single-photon source for satellite communications

Quantum communication protocols, such as teleportation, entanglement swapping, and quantum key distribution, are fundamental for the security of communications, based on the laws of quantum mechanics. Photons are the preferred information carriers, especially for long-range transmissions through satellite links. These protocols demand single-photon sources with stringent requirements in terms of brightness, bandwidth, and wavelength, depending on the application. This thesis presents a source for space-to-ground communication, operating at a wavelength of 1560 nm, and employing two cascaded nonlinear crystals to generate ultra-narrow-bandwidth photon pairs at 1560 nm and 780 nm. It discusses the difficulties encountered on the optical table, in particular in coupling light and characterising the crystals, and the techniques devised to address them. It concludes with an overview on future work and potential applications.