Pragmatic Quantum Cryptography in Next-Generation Photonic Networks

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Humanity’s understanding of quantum physics has finally reached the level where it can be harnessed to revolutionise society. Radical new technologies will transform a wide range of fields that rely on sensing, imaging, information processing and communications. In particular, quantum computers will be able to run algorithms that offer a substantial advantage over their classical counterparts in trying to solve some of the world’s hardest problems. However, there is an equally significant cost, as this allows attackers to break the public-key cryptography that underpins both our daily lives and our critical infrastructure.

Quantum key distribution is one possible defence. It uses single photons to transmit cryptographic keys, with security reliant on the principles of quantum mechanics. Here, we will endeavour to overcome some of the challenges that manifest when trying to deploy such a technology in everyday networks. We present the first demonstration of quantum key distribution as part of a software-defined architecture, ensuring compatibility with future infrastructure, and incorporating time-division multiple access to reduce implementation costs. In addition, the development of a hybrid quantum/post-quantum network acts as a first step towards ensuring quantum key distribution does not remain an isolated technology.

We also counteract a particularly devastating denial of service attack through the invention of a new protocol, established on the basis that information-theoretically secure encryption remains impractical even when the keys are supplied by a quantum device. A wide range of theoretical and experimental evidence is used to support this hypothesis. Finally, we advance the state-of-the-art in chip-to-chip quantum key distribution, using wavelength-division multiplexing to introduce additional flexibility and maximise the secret key rates.
Date of Award19 Mar 2019
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorJohn G Rarity (Supervisor) & Chris Erven (Supervisor)

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