UV-C short-range wireless quantum key distribution

Thesis

The rapid advancement of quantum technology increases the security risks of conventional encryption schemes, such as the Rivest-Shamir-Adleman (RSA) algorithm. Quantum key distribution (QKD) has emerged as a secure cryptographic solution, using Heisenberg’s uncertainty principle and the no-cloning theorem to ensure unconditional security in key exchange. Significant progress has been made in fibre-based and satellite QKD systems, achieving long transmission distances and high secure key rates (SKR). However, short-range wireless QKD remains largely unexplored, primarily due to severe ambient light interference, which degrades system performance and limits practical deployment.

This thesis reports a short-range wireless QKD operating in the ultraviolet-C (UV-C) spectrum, utilizing the solar-blind region to mitigate ambient light interference. A high-sensitivity UV-C receiver was developed using a cooled silicon photomultiplier (SiPM), enabling a 1 Mbit/s optical wireless communication (OWC) link. Subsequently, ultralow photon flux links were demonstrated using a UV-C micro-LED and a single-photon detector (SPD), achieving a maximum data rate of 120 Mbit/s with a minimum transmitted photon number per bit of 7.7. Finally, the world’s first wireless QKD system operating in the UV-C region was implemented, inferring an SKR exceeding 1 Mbit/s. Additionally, the impact of LED-based ambient light and sunlight interference was analysed, and mitigation strategies were proposed to enhance system robustness.

Overall, this work establishes the feasibility of UV-C wireless QKD and provides a foundation for future improvements in ambient light rejection and real-world deployment.

Authors: Liu, F

• DOI: 10.5287/ora-zbn1y2v1v
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Quantum Key Distribution; Optical Wireless Communications; Ultraviolet C
• Subjects: Optical communications