Quantum Causal Models, Faithfulness, and Retrocausality

Abstract Wood and Spekkens ([2015]) argue that any causal model explaining the EPRB correlations and satisfying the no-signalling constraint must also violate the assumption that the model faithfully reproduces the statistical dependences and independences—a so-called ‘fine-tuning’ of the causal parameters. This includes, in particular, retrocausal explanations of the EPRB correlations. I consider this analysis with a view to enumerating the possible responses an advocate of retrocausal explanations might propose. I focus on the response of Näger ([2016]), who argues that the central ideas of causal explanations can be saved if one accepts the possibility of a stable fine-tuning of the causal parameters. I argue that in light of this view, a violation of faithfulness does not necessarily rule out retrocausal explanations of the EPRB correlations. However, when we consider a plausible retrocausal picture in some detail, it becomes clear that the causal modelling framework is not a natural arena for representing such an account of retrocausality. 1 Causal Models, Quantum Mechanics, and Faithfulness2 Fine-Tuning 2.1 Fine-tuning in a retrocausal model3 Possible Responses4 Quantum Causal Models and Retrocausality 4.1 A more detailed retrocausal account 4.2 A model of the EPRB probabilities 4.3 Mapping to a causal model5 Conclusion