Causal Modelling for Quantum Foundations: Past, Present, and Future
Bell’s Theorem shows that the predictions of quantum theory are in conflict with the natural assumptions of local realism. In this overview talk I’ll explain why Bell’s Theorem can be thought of a special result within the formal science of causes and effects, namely causal inference. I’ll explore a variety of causal structures beyond the Bell Scenario, exploring some of the constraints each such causal structure implies on observable statistics. In an effort to recognize which constraints can be violated by quantum theory (analogs of Bell inequalities) and which cannot, I’ll introduce the inflation technique for causal inference. I’ll also consider the causal modelling framework in which unobserved nodes can represent nonclassical common causes, be they quantum or post-quantum. I’ll argue that nonclassical causal structures suggest a natural framework for thinking about genuinely multipartite nonlocality substantially different from the conventional framework motivated by LOCC entanglement.