Quantum reference frames and relationalism in quantum theory

          @misc{ pirsa_PIRSA:08090075,
            doi = {10.48660/08090075},
            url = {https://pirsa.org/08090075},
            author = {Bartlett, Stephen},
            keywords = {Quantum Foundations},
            language = {en},
            title = {Quantum reference frames and relationalism in quantum theory},
            publisher = {Perimeter Institute},
            year = {2008},
            month = {sep},
            note = {PIRSA:08090075 see, \url{https://pirsa.org}}
          }
          

Abstract

A reference frame can be treated as a physical quantum object internal to the theory. Quantum reference frames whose size, and therefore accuracy, are bounded in some way necessarily limit one\'s ability to prepare states and to perform quantum operations and measurements on a system. The nature of these limitations is similar in many ways to that of decoherence. We investigate how a quantum reference frame of bounded size can be \'dequantized\', i.e., treated as external to the quantum formalism, in such a way as to induce an effective decoherence on any system described relative to it. In particular, we show that this decoherence has an interpretation as a lack of classical information about an ideal (infinite size) reference frame.