Enhancements to quantum communication performance utilizing a prototype photonic lantern and multiplexed single-photon detection

Detection in free-space quantum key distribution is typically performed by coupling light into an optical fiber coupled single-photon detector. However, use of multimode fibers will limit the achievable bandwidth due to modal dispersion, depending on the length and core diameter. We demonstrate a novel approach to overcoming the bandwidth limitation, while still maintaining efficient coupling, utilizing a prototype multimode fiber-based photonic lantern to interface numerous detectors. As the lantern splits light into multiple smaller core diameters, it also reduces the impact of modal dispersion. Moreover, we show secret key rate enhancement up to 20% with the multimode fiber photonic lantern.