# Quantum information and foundations

Our research in quantum information and foundations ranges from the abstract to the concrete, covering both applications and conceptual aspects of quantum theory.

On the one hand we are working towards a deeper understanding of puzzling features of quantum theory such as indeterminacy, entanglement, non-locality and contextuality. On the other hand, we are exploiting these fundamental ideas for information-processing tasks such as quantum cryptography and quantum computing.

Our group is part of the York Centre for Quantum Technologies and some of our members work in the UK Quantum Technologies Hub for Quantum Communications. We also collaborate with experimentalists at the National Physical Laboratory. Some topics of focus currently include:

### Causation in quantum theory

One way to interpret Bell’s theorem is that it shows that classical notions of causation are not fit for purpose in light of quantum theory. We are investigating notions of causation for quantum theory and how they differ from the classical ones.

### Quantum contextuality

The Kochen-Specker theorem shows that even single quantum systems are difficult to reconcile with classical thinking, due to a property called quantum contextuality. We are exploring various forms of quantum contextuality as well as seeking applications for information processing tasks.

### Quantum random number generation

Assessing the quality of a random number generator requires a detailed understanding of the physical process by which the numbers were generated. Through collaboration with experimentalists at the National Physical Laboratory we are assessing commercial and prototype quantum random number generators with a view to certifying how much quantum randomness they are generating. We are also developing device-independent protocols which aim to prove security without the need to know how the devices being used work.

### Foil theories of quantum mechanics

Both Classical Mechanics and Quantum theory represent specific cases within the family of so-called General Probabilistic Theories. An intriguing question is to identify physical principles that would allow us to single out quantum theory within this class of structurally similar theories. Other foil theories can be obtained by assuming that the standard projection postulate takes a different form.