Speaker
Description
Three foundational aspects will be discussed in which relational approaches offer insight into developing a background-independent description of quantum spacetime: the notions of events, diffeomorphisms and the assumption underlying quantum probability assignments. The first aspect concerns the notion of events and their localisation, which fundamentally differ in quantum theory and general relativity. We propose an operational approach drawing from quantum information and apply it to the quantum switch (QS); this analysis reveals differences between classical and quantum spacetime realisations of QS, clarifies a longstanding interpretational debate, and demonstrates how different conclusions stem from distinct assumptions. The second aspect addresses diffeomorphisms in regimes beyond superpositions of semiclassical spacetimes; I will briefly present a construction of quantum diffeomorphisms for linearised quantum gravity, along with their physical implications and their role in realising background independence. The third concerns a basic assumption in quantum probability assignments, that experimental data arise from an identically and independently distributed (i.i.d.) ensemble; this assumption is expected to break down in certain regimes of quantum gravity. I will outline a proposal to resolve this issue by leveraging the tool of quantum reference frames in the measurement context.
