Quantum Reference Frames in Spacetime (Viktoria Kabel, IQOQI Wien)

When describing a physical system, it is very common to do so with respect to a reference frame – a ruler used to determine the position of a particle, for example, or a clock, which tracks the time that elapses while it is moving. Usually, reference frames are treated as purely classical objects with well-defined properties. But what happens if we take into account the quantum properties of the reference frame itself? In this talk, I will give an introduction to the basic idea and formalism of quantum reference frames, which aims to address this question. Moreover, I will discuss their connection to gravity from two different angles. Firstly, how an invariance under quantum reference frame transformations can help us understand scenarios at the interface between quantum physics and gravity from a new perspective. Secondly, how quantum reference frames can be seen to emerge naturally as edge modes at the boundary of spacetime in linearised general relativity.