Speaker
Description
Abstract:
In standard textbook treatments, reference frames serve merely to describe physical situations and are taken to be external to the systems under study. Yet many physically relevant settings — such as those encountered in gauge theories, gravity, or quantum communication — lack any meaningful external frame. This raises the question of how to describe physics in the absence of such a structure.
The answer lies in adopting internal reference frames: subsystems that transform non-trivially under the symmetry group of interest and provide the means to describe physical systems “from the inside” in purely relational terms. This perspective embodies the idea that all reference frames are associated with physical systems and are therefore ultimately quantum — so-called quantum reference frames (QRFs). QRFs are thus essential for describing and extracting physics whenever no external reference frame for a given symmetry group is available. This situation arises most prominently for gauge symmetries, as in gauge theory and gravity, where QRFs appear naturally in the construction of physical observables and in the definition of a relational notion of locality and gauge-invariant subsystems. The choice of an internal QRF is typically non-unique, leading to a novel notion of quantum covariance of physical properties under QRF transformations.
In this talk, I’ll review the basic ideas and tools of the QRF program, with particular emphasis on the so-called perspective-neutral framework for quantum frame covariance. I will conclude by discussing recent developments and some open questions in this broad and active area of research.