Cost and efficiency comparison of Quantum Key Distribution schemes

Abstract: The development of quantum computing exposes critical vulnerabilities in classical encryption systems. However, quantum computing also enables new methods of secure communication. Quantum key distribution (QKD) is one class of such methods. Quantum key distribution enables the secure generation and transfer of cryptographic keys, while not sharing the vulnerabilities of classical systems. This thesis compares three QKD schemes: BB84, E91 and B92. Specifically, the schemes are evaluated with regards to quantum cost, a measure of the resources needed to construct a quantum system, and raw key efficiency, which describes the efficiency of key transfer. The schemes were simulated in ideal, noiseless conditions on a classical computer, yielding their mean raw key efficiencies. Scheme implementations were designed and analysed according to a pre-existing cost metric, yielding their quantum costs. We conclude that BB84 is the most cost-efficient of the three schemes. B92 is a low-cost option, although less efficient than BB84. E91 is an unjustifiable option, having a higher cost than BB84, but not outperforming its raw key efficiency.