Philosophy of Physics Seminar (Thursday - Week 8, MT24)

Abstract: As Timotheus Riedel notes in a recent paper, over the past few years, a flurry of related no-go results in extended Wigner’s friend scenarios has been taken to place strong constraints on the possibility of absolute facts about the outcomes of quantum measurements. In my pragmatist view a system’s quantum state, and the outcome of a measurement on it, are each relative—not to “the observer” but to something physical. I shall explain what this means, how my view differs from Rovelli’s relational quantum mechanics, and why this perspective on quantum theory is not refuted by arguments based on extended Wigner’s friend scenarios, including Riedel’s.