PhD Defense - Nicholas Gauguin Houghton-Larsen

Title:  A Mathematical Framework for Causally Structured Dilations and its Relation to Quantum Self-Testing

Abstract:

Quantum theory constitutes our best scientific understanding of the world. However, the mathematical formalism behind it is technical and particular. A certain phenomenon in quantum theory (namely self-testing) is concerned with the following question: How do different implementations of the same physical process compare to each other?  The conventional definition of self-testing is cast in the technical, particular formalism behind quantum theory, but this is strange since the question seems meaningful and relevant much more broadly.

 In the PhD thesis, I present a mathematical framework in which one can indeed argue about the above question very generally and without relying on a specific formalism for the underlying theory. (A framework of this kind is often called “operational”.) In the framework, physical processes are modelled by causally structured information channels, and implementations by so-called dilations of these channels. The phenomenon of self-testing, which originally motivated the thesis, corresponds to a special case, so the results of the thesis point in particular towards the first known operational definition of self-testing.

 During the defence, I will discuss core ideas in the framework and the connection to quantum self-testing. Parts of the talk will address a general audience.

link to the thesis

Supervisor:

Matthias Christandl (University of Copenhagen)

Assessment Committee:

Roger Colbeck (University of York, UK)

Tobias Fritz (University of Innsbruck, Austria)

Nathalie Wahl (University of Copenhagen, Denmark) Chair