Causal Graphs for EPR Experiments

We examine possible causal structures of experiments with entangled quantum objects. Previously, these structures have been obscured (i) by assuming a misleading probabilistic analysis of quantum non locality as 'Outcome Dependence or Parameter Dependence' and (ii) by directly associating these correlations with influences. Here we try to overcome these shortcomings: (i) we proceed from a recent stronger Bell argument (Näger 2012), which provides an appropriate probabilistic description, and (ii) apply the rigorous methods of causal graph theory. Against the standard view that there is only an influence between the measurement outcomes, we show that there must be an influence from one setting (parameter) to its distant outcome: EPR correlations can only come about if one of the outcomes is a common effect of both settings. \ud Our discussion makes explicit under which assumptions similar conclusions from information theoretic considerations (Maudlin 2002, ch. 6; Pawlowski et al. 2010) can be interpreted causally