High-dimensional and multiplexed schemes for fiber-based quantum key distribution protocols.

Quantum key distribution protocols are easily the most advanced quantum information technology up to date, driving the whole field of quantum communications towards actual systems implementations and flourishing theoretical advances and
experimental demonstrations. Exploiting the consolidated telecommunications industry knowledge, optimized equipment and already existing broad infrastructure, fiber-based quantum key distribution schemes are in particular a promising direction
in which the scientific research efforts are addressed, for the final goal of building a quantum network. However, three main challenges are still preventing the large-scale industrial deployment of fiber-based quantum key distribution schemes: the limited
achievable secret key generation rate, when compared to those reached by classical communications; the bounded propagation distances, due to intrinsic channel losses; and the struggle of the integration with classical data rates, which are additional
sources of noise from the point of view of a quantum channel. During my Ph.D., we have focused on two of these problems, proposing new efficient designs for fiber-based high-dimensional protocols and space division multiplexing schemes to increase the secret key rate of quantum systems, and investigating the optimization of wavelength multiplexing setups for the integration with classical communications.