School on Quantum Computation

According to one of the most fundamental symmetries in physics, an observer on a moving train applies the same laws to describe a physical system as an observer standing on the platform - the form of the physical laws is invariant when choosing a frame of reference. However, reference frames such as the train and the platform are physical systems and therefore ultimately obey quantum mechanical laws. In particular, they could be in a quantum state of superposition of different positions or momenta. So what would the description of physical systems look like to an observer in such “quantum reference frames” (QRF)? Are the forms of physical laws invariant when changing QRFs? I will introduce the notion of QRFs and show how they help us to address some open problems in relativistic physics and in typical quantum gravity situations.