Advances in Chip-Based Quantum Key Distribution

Abstract

Technology founded in quantum phenomena is set to revolutionise computation, sensing and communication. With an entirely different method of manipulating information, quantum computers in particular are able to offer significant advances when compared to their classical counterparts. Unrelenting research throughout the world implies that such machines are set to be the demise of public-key cryptography that is critical to modern society.

Quantum key distribution (QKD) offers a method to securely distribute randomness between distant parties using the fundamental nature of the universe. Protocols do not depend on assumed hard problems and so the security of the key does not decrease as computing power increases. However, QKD systems have been susceptible to information leakage or hacks which compromises their security at the time of key exchange. As research demonstrations evolve into commercial systems, the security of a physical implementations must be addressed.

Device-independent protocols have since been introduced to relieve the possibility of secret information falling into the hands of an adversary. Using correlations between random events, the physical system does not contain any information about the key. Therefore, it is not susceptible to attacks or able to reveal the secret key. This simplifies the task of characterising a system to guarantee a secure key exchange.

Before QKD can be widely adopted, a cost-effective and scalable platform must be developed. In the last decade, photonic integration has been refined to facilitate circuit complexity simply not possible with bulk alternatives. The inherent robustness and phase-stability make it an excellent candidate for future quantum-secured networks.

This thesis will explore how integrated photonics can be deployed in device-independent QKD protocols to both ensure practical security and enhance network accessibility. We will show how integrated components can be used to generate quantum states with high fidelity and demonstrate quantum interference. The complexity of photonic integration will be explored to demonstrate new circuits for QKD that will eventually form the backbone of quantum-secured networks.

Date of Award	12 May 2020
Original language	English
Awarding Institution	University of Bristol
Supervisor	Jorge Barreto (Supervisor) & Chris Erven (Supervisor)