Quantum reference systems: Where foundations meets gravity

          @misc{ pirsa_PIRSA:18070052,
            doi = {10.48660/18070052},
            url = {https://pirsa.org/18070052},
            author = {Hoehn, Philipp},
            keywords = {Quantum Foundations},
            language = {en},
            title = {Quantum reference systems: Where foundations meets gravity},
            publisher = {Perimeter Institute},
            year = {2018},
            month = {aug},
            note = {PIRSA:18070052 see, \url{https://pirsa.org}}
          }
          

Abstract

Quantum foundations and (quantum) gravity are usually considered independently. However, I will demonstrate by means of quantum reference systems how tools and perspectives from quantum gravity can help to solve problems in quantum foundations and, conversely, how quantum foundation perspectives can be useful to constrain spacetime structures. First, I will show how one can derive transformations between quantum reference frames from a gravity inspired symmetry (essentially Mach’s) principle. This principle enforces a perspective neutral theory in which choosing the perspective of a specific frame becomes a choice of gauge and all physical information is relational. This setting enables one to derive and generalize, from first principles, frame transformations that have been proposed earlier in the foundations literature. Moreover, the framework extends to the relational paradigm of dynamics, familiar from quantum gravity, and thereby provides a unifying method for changes of perspective in the quantum theory, incl. changes of both spatial and temporal quantum reference systems. Subsequently, I will take a quantum information inspired perspective on frame synchronization and transformations. Without presupposing specific spacetime structure, I will exhibit how the Lorentz group follows from operational conditions on quantum communication, exemplifying how quantum information protocols can constrain the spacetime structures in which they are feasible.