A PhD position is available in the Department of Mathematics at the University of York to work with Roger Colbeck on quantum random number generators (QRNGs). Random number generators are useful in a wide variety of applications. Quantum processes are needed to generate fundamental randomness. One of the difficulties in quantum random number generation is being confident that the process being used really can generate randomness. The usual way of doing so involves taking the random number generator apart and modelling each of its internal components in detail.