Nonlocal and Relativistic Protocols for Quantum Cryptography

Recently, decided steps have been taken towards increasing the performance of quantum processors to a point where they can outperform modern supercomputers at certain tasks. In light of this, it seems reasonable to expect the first generation of quantum computers to be created within the next few years. The importance of cryptographic protocols that are secure against quantum attacks is therefore apparent.

Numerous quantum cryptographic protocols have already been suggested, spanning a wide range of cryptographic tasks, however many of these rely on impractical assumptions about the resources available to the parties involved. This project aims to exploit the fundamentally nonlocal nature of quantum mechanics to build improved protocols for a variety of cryptographic tasks, with a focus on the practicality of their assumptions. The potential cryptographic power of relativity theory (in particular, the impossibility of faster-than-light communication) in this context will also be examined.

The project will initially centre upon the generation of truly random numbers by untrusted devices, whose randomness is certified by quantum mechanics. Both numerical and theoretical techniques will be employed to probe the possibility of using a certain practical class of games, played between multiple parties, to achieve this certification. More generally, the utility of protocols for the self-testing of quantum devices, whereby one wishes to verify the existence of a particular quantum state from only the measurement outcome statistics of the device, will be extended.