Hi all,
Tomorrow our visitior Thomas Galley will tell us about ''Quantum reference frames for general groups in the perspective neutral approach: the role of symmetry and gauge''. See below for the abstract. The talk will take place at 2pm in F 31.1 or on Zoom: https://ethz.zoom.us/j/362994444.
Best, Ladina
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Title: Quantum reference frames for general groups in the perspective neutral approach: the role of symmetry and gauge.
Abstract Quantum reference frames are used to obtain a description of a certain subset of physical subsystems relative to a reference system, in the absence of external relata. In this talk I will first introduce changes of quantum reference frames for general groups in the “purely perspective dependent” approach. Following this I will show how to derive changes of quantum reference frames for general groups from a “perspective neutral state” which is a state which encodes all the different perspectives. In this approach one begins with a physical Hilbert space which is invariant under the action of the gauge group G. One can recover the perspective of a given reference system from a physical state via a conditioning map. The perspective dependent states obtained via this conditioning map lie in a space called the reduced physical Hilbert space of the subsystems relative to the reference system. The reduced Hilbert of a given subsystem naturally depends on the choice of reference system. One can recover changes of quantum reference frame between different perspectives via these conditioning maps and their inverses. In a final part of the talk I discuss in more detail the difference between gauge and symmetry, and show that in the case where there is an action of the gauge group only, then the reduced Hilbert space of a given subsystem is not just dependent on the choice of reference frame, but also the orientation of that reference frame.