Conference

The approach to quantum theory known as QBism notoriously asserts that the quantum state is not even a partial representation of reality, but instead quantifies an agent's subjective degrees of belief about future experiences. Despite its counter-intuitive premise, QBists argue that this interpretation has the potential to illuminate and demystify certain aspects of quantum theory. In this talk I will discuss how `causality' might be interpreted by a QBist, and whether doing so might help us understand the bizarre hypothetical phenomenon of `indefinite causality'.

The possibility of indefinite causal order has garnered considerable interest in recent years, both for its promise as a resource, e.g. for communication, and for its role in exploring the fundamental physical constraints on causal structure. In order to gain a better understanding of the phenomenon, one approach is to design experiments that implement – or at least simulate – scenarios with indefinite causal order. While post-selection is one way to simulate exotic causal structures, this approach may not provide the desired insights. Instead, I will discuss how one might go about implementing indefinite causal order without post-selection.