PIRSA:13040124

Quantum measurements constrained by symmetry

Loveridge, L. (2013). Quantum measurements constrained by symmetry. Perimeter Institute. https://pirsa.org/13040124

Loveridge, Leon. Quantum measurements constrained by symmetry. Perimeter Institute, Apr. 30, 2013, https://pirsa.org/13040124 

          @misc{ pirsa_PIRSA:13040124,
            doi = {10.48660/13040124},
            url = {https://pirsa.org/13040124},
            author = {Loveridge, Leon},
            keywords = {Quantum Foundations},
            language = {en},
            title = {Quantum measurements constrained by symmetry},
            publisher = {Perimeter Institute},
            year = {2013},
            month = {apr},
            note = {PIRSA:13040124 see, \url{https://pirsa.org}}
          }

Leon Loveridge University of York

Talk numberPIRSA:13040124
DOI10.48660/13040124
Collection
Talk Type Scientific Series
Subject

Abstract

The Wigner-Araki-Yanase (WAY) theorem delineates circumstances under which a class of quantum measurements is ruled out. Specifically, it states that any observable (given as a self adjoint operator) not commuting with an additive conserved quantity of a quantum system and measuring apparatus combined admits no repeatable measurements. I'll review the content of this theorem and present some new work which generalises and strengthens the existing results. The observation that the WAY constraint vanishes if the observable-to-be-measured is ``relativised'' (in a suitable sense) points to interesting links with quantum reference frames and superselection rules. I'll discuss some of these connections and raise some open questions.