Thursday, 30 June 2022 @ 12 PM in 149 Keck Center, or join us on Zoom.

Abstract: Quantum Theory requires a background causal structure for its formulation, with temporal and spatial correlations treated in a very asymmetric way. However, spacetime might lose its classical properties  when Quantum Theory combines with General Relativity. This motivates a more general framework where causal relations are not set a priori. A further motivation comes from distributed networks, where the causal order of events might not be known in advance. I will present a formalism that posits the local validity of quantum mechanics locally but does not assume a global causal structure. Besides reproducing all standard quantum scenarios, the formalism predicts novel, “indefinite” causal relations. Such causal relations can be realised in thought experiments involving superpositions of spacetime metrics, but also describe laboratory experiments with events delocalised in time, opening the way to novel resources for computation and communication. Finally, the same formalism provides a natural framework to describe non-Markovian quantum processes, resolving an open problem in the study of open quantum systems.