Hi all,
tomorrow we'll hear from Nuriya Nurgalieva on her master's thesis. The
title and abstract follow. We should also discuss whether Monday at
4pm will be a convenient meeting time for everyone this semester.
Best,
-joe
Title: Quantum reference frames for experiments where observers can be measured
Abstract: Frauchiger and Renner recently proposed an expansion of
Wigner’s friend experiment to prove that single-world interpretations
of quantum theory cannot be self-consistent. Experimenters are modeled
as agents who use quantum theory, and additionally can themselves be
measured as physical systems. However, Frauchiger and Renner’s
description of the experiment implicitly assumes that all agents have
access to perfect, classical reference frames. In doing so it imposes
artificial classicality on a setting that tries to model only quantum
evolutions, and risks missing out on subtleties that could explain the
paradox. We model each lab as a system which consists of a spin, a
reference frame and an agent’s memory, evolving under a unitary.
Concretely, we investigate whether different agents refer to the same
degrees of freedom and quantum subsystems when they talk about the
outcome of a measurement. Our results show that in the setting with
the finite reference frames agents are not able to make deterministic
predictions.