We present a causal model for the EPR correlations. In this model, or better framework for a model, causality is preserved by the direct propagation of causal influences between the wings of the experiment. We show that our model generates the same statistical results for EPR as orthodox quantum mechanics. We conclude that causality in quantum mechanics can not be ruled out on the basis of the EPR-Bell-Aspect correlations alone.
We present a causal model for the EPR correlations. In this model, or better framework for a model, causality is preserved by the direct propagation of causal influences between the wings of the experiment. We show that our model generates the same statistical results for EPR as orthodox quantum mechanics. We conclude that causality in quantum mechanics can not be ruled out on the basis of the EPR-Bell-Aspect correlations alone.
There has been an intense discussion, albeit largely an implicit one, concerning the inference of causal hypotheses from statistical correlations in quantum mechanics ever since John Bell’s first statement of his notorious theorem in 1966. As is well known, its focus has mainly been the so-called Einstein-Podolsky-Rosen (“EPR”) thought experiment, and the ensuing observed correlations in real EPR like experiments. But although implicitly the discussion goes as far back as Bell’s work, it is only in the last two decades that it has become recognizably and explicitly a debate about causal inference in the quantum realm. The bulk of this paper is devoted to a review of three influential arguments in the philosophical literature that aim to show that causal models for the EPR correlations are impossible, due to Bas Van Fraassen, Daniel Hausman and Huw Price. I contend that all these arguments are inconclusive since they contain premises or presuppositions that are false, unwarranted, or at least controversial. Five different common cause models are outlined that seem perfectly viable for the EPR correlations. These models are then employed to illustrate various difficulties with the premises and presuppositions underlying Van Fraassen’s, Hausman’s and Price’s arguments. In all these cases it is argued that the difficulties cut deep against these authors’ own theories of causation and causal inference. My conclusions are that causal models for the EPR correlations remain viable, that philosophical work is still required to assess their relative virtues, and that in any case the mere theoretical conceivability and empirical possibility of these models sheds doubts over Van Fraassen’s, Hausman’s and (important elements in) Price’s theories of causation and causal inference.
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. 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.
This Ph.D. thesis is about causality in Quantum Mechanics, namely about the possibility to provide a causal explanation for quantum Einstein – Podolsky – Rosen (EPR) correlations.The well-known interpretation of the Bell’s Theorem by Bastian Van Fraassen, who inferred that quantum correlations cannot be embedded in any causal model, compels us to suppose that microscopic nature cannot have a causal structure and that causality is an anthropological concept.However, this interpretation is not commonly accepted and this doctoral thesis is the first general overview of some recent works about causal explanation for EPR correlations. Particularly, it analyses the possible causal explanations for the EPR/Bohm experiments by means of the Hans Reichenbach’s model, by means of backward causation models, and by means of models that imply a direct causal link. In order to do it, it pays particular attention to the Relativistic space-time features and it considers the studies in the History of Philosophy about the link between causal arrow and temporal arrow. Moreover, this work aims to endorse the idea that the best way to explain EPR/Bohm correlations causally is to adopt an indeterministic non-Reichenbachian common cause model, particularly Cartwright’sgeneral forksmodel.My conclusion is that causal models for quantum correlations remain viable, and that there is no contrast between genuinely indeterministic interpretation of Quantum Theory and causal explanation, with the philosophical implication that the Causal Realism is still acceptable.
It has been claimed that quantum mechanics is a non-local theory, i.e., that the predictions of quantum mechanics are at odds with a conception of the world where all the interactions are mediated by local mechanisms. The cited reason is the violation of the Bell inequality in cases where measurements are performed on quantum systems of particles that have interacted in the past. Quantum mechanics predicts that the state of the particles in such a system are correlated, a result obtained from considering a thought-experiment often known as EPR. In this thesis, I will argue that the violation of the Bell inequality in EPR forces us to either accept that causes sometimes act both backwards and forwards in time, or give up some widely-held assumptions about causal relations or the role of causal explanations. First, I will present three principles regarding causality that I take be widely accepted. I will then present the background for the claim the quantum mechanics is a non-local theory, and discuss the implications of non-local causal influences in light of the Special Theory of Relativity. One argument against a causal explanation of the EPR-correlations will be discussed, and different models for the causal structure of EPR will be assessed. I will argue that a retrocausal model – models that include instances of retrocausation, where the direction of causation is the opposite of the direction of time – is the only viable option if we want to uphold the three principles presented in chapter 1. I will discuss the plausibility of rejecting one of these principles, and argue that at least one of the can be restricted in a way that still accounts for our commitment to it. Finally, I will assess the non-local models against the retrocausal models, and argue that a retrocausal model offers interpretational advantages over the non-local alternatives.
Quantum mechanics has achieved unparalleled success as an operational theory, describing a wide range of experiments to remarkable accuracy. However, the physical foundations on which it rests remain as puzzling as they were a century ago, and a concise statement of the physical principles that underlie quantum mechanics is still outstanding. One promising approach holds that these principles should be formulated in terms of information, since many of the counter-intuitive effects in quantum theory concern questions such as what one can know about a quantum system and how the information encoded therein can be processed and distributed between parties. Another challenging feature of quantum theory is its incompatibility with the other cornerstone of modern physics, general relativity. In order to reconcile the two, one must identify and retain only the essential concepts and principles of each theory, and in the case of general relativity, causality has been identified as such a concept. This raises the question of how our classical understanding of causality must change when quantum theory is taken into account. In order to address these questions about information, knowledge and causality, I turn to the framework of causal models. In classical statistics, causal models explain the relations among a set of variables in terms of causal influences, which makes them a powerful tool for structuring our knowledge about complex systems and developing strategies for interacting with them. More importantly, the framework provides the conceptual underpinnings and mathematical methods for addressing questions about causation, information and knowledge in a rigorous manner. In this thesis, I develop a version of the classical causal models framework that is compatible with quantum theory and explore its physical implications. \n \n \nA first step is to define quantum versions of fundamental elements such as variables, conditionals and belief propagation rules. This allows one to consider the question of what one can come to know about a quantum variable from the point of view of causal modelling. The conditionals relating quantum variables are found to have a richer structure than their classical counterparts, which can be exploited for the task of discerning causal relations given limited data -- a central problem in classical causal modelling. The mathematical properties of quantum conditionals also establish a correspondence between various classes of two-party correlations, such as bound and distillable entanglement, and the types of causal structures that can give rise to them, which may become a useful tool for entanglement theory and quantum information processing. In the context of open quantum systems dynamics, quantum causal models provide a clear physical explanation of not completely positive maps and, more broadly, of non-Markovian quantum dynamics. Finally, I consider the possibility of non-classical effects in the way that different causal mechanisms are combined -- that is, non-classical causal structures. For the simple case of two causally ordered variables, I propose indicators that witness different classes of combinations of causal mechanisms, including a non-classical mixture, and describe an experiment realizing examples of the different classes. \n \n \nAs these results illustrate, the framework of quantum causal models provides both greater conceptual clarity and a comprehensive mathematical formalism for studying a diverse set of problems, ranging from foundational questions to applications in open systems dynamics and the exploration of non-classical causal structures, which are likely to feature in a future theory of quantum gravity. The material presented in this thesis is intended as a foundation and inspiration for further applications of quantum causal models.