Quantum Reference Frames: From Quantum Information to Gravity

by Viktoria Kabel (ETH Zurich)

Monday 27 Oct 2025, 14:00 → 15:00 Europe/Rome

Aula Grassano

Symmetries pervade our physical theories, from classical general relativity to quantum theory. As a consequence, only relational quantities are deemed physically meaningful. One way to construct such relational quantities is to choose some degrees of freedom as a reference frame and to express everything else relative to them. This leads to a description in terms of relative distances for simple translation-invariant theories, dressed observables in gauge theory, and relational observables in general relativity. When considering the quantisation of these theories, we might also want to take into account the quantum properties of the reference frames themselves. This leads to the notion of a quantum reference frame (QRF). Due to the ubiquity of symmetries, QRFs lie at the intersection of several different fields: from quantum information theory to quantum gravity. As such, they offer to provide a bridge between otherwise separate communities. In this talk, I will focus on QRFs in the context of linearised (quantum) gravity, where they can be related to edge modes - additional degrees of freedom at the boundary of a spacetime region - relational observables, and might even provide a way to regularise gravitational entropies in the perturbative regime.