Exploring the Performance of Structured Light Modes and Novel Protocols for Quantum Key Distribution

Abstract

This thesis includes two main projects that explore the use of structured light, especially photonic orbital angular momentum (OAM), in quantum key distribution protocols. Particular attention has been paid to how different modes behave in turbulent channels and how adaptive optics systems can mitigate the distortions induced in the beam. Based on the results of these experiments, we propose a new protocol designed to combine the qualities that make a light mode ideal for turbulent channels and adaptive optics systems. The security analyses and performance evaluations of this new protocol are discussed.

In the first chapter, a brief overview of the field is provided. Following that, the second chapter aims to explore the necessary background for understanding the two projects in more detail. We discuss the different degrees of freedom of light and how they can be utilised to help achieve our goals. In the third chapter, the mathematical background relevant to the first project is covered. This includes the modes investigated in the turbulent channel and AO system. In the fourth chapter, an overview of the theory of security in quantum key distribution is presented, followed by an article on a new protocol for QKD. Finally, the conclusions and outlooks are outlined in the last chapter.