On quantum entanglement, counterfactuals, causality and dispositions

Abstract

The existence of non-local correlations between outcomes of measurements in quantum entangled systems strongly suggests that we are dealing with some form of causation here. An assessment of this conjecture in the context of the collapse interpretation of quantum mechanics is the primary goal of this paper. Following the counterfactual approach to causation, I argue that the details of the underlying causal mechanism which could explain the non-local correlations in entangled states strongly depend on the adopted semantics for counterfactuals. Several relativistically-invariant interpretations of spatiotemporal counterfactual conditionals are discussed, and the corresponding causal stories describing interactions between parts of an entangled system are evaluated. It is observed that the most controversial feature of the postulated causal connections is not so much their non-local character as a peculiar type of circularity that affects them.

Understanding quantum mechanics: a review and synthesis in precise language

“…These features strongly resemble features of classical physics in which the term correlation might be used without controversy. It is therefore common to refer to correlations in this context, and to explore their implications in terms of causation [327]. There are, however, reasons to doubt that such an approach is appropriate.…”

“…Bohmian relating to the approach suggested by de Broglie and developed by Bohm; see Sect. 6.2 causal generally defined relative to a specific theoretical model [555][556, § 3][557, § 4]; causal notions are not necessarily needed to achieve understanding [38]; even where they are invoked, there is no consensus on how causation is to be defined [327][558, § 2] [559] coherence (for waves) the absence of spatial dispersion; (for superposition states) the existence of interference terms [234]; (for entangled states) statistical balance in collective outcomes, among ensembles for measurements of differing observables on multiple subsystems [235, § 2.3]: see Sects. 3.5 and 3.6 completeness feature of a theory with terms which specify all the properties of a system [53] contextuality generally defined relative to one specific approach to quantum mechanics [328, § V.E] [371]; broadly, assignment of values depends on the relevant measurement process [306]; see Sect.…”

“…3.5 and 3.6 completeness feature of a theory with terms which specify all the properties of a system [53] contextuality generally defined relative to one specific approach to quantum mechanics [328, § V.E] [371]; broadly, assignment of values depends on the relevant measurement process [306]; see Sect. 5.7 counterfactual (formal) a subjunctive conditional sentence, whose antecedent is contrary-to-fact [558]; (informal) relating to circumstances being other than as they are [30]; a complex area [327] decoherence absence of coherence; the disappearance of the interference terms in a density matrix representing a superposition state; see Sect. 4.4 density matrix a matrix, with specific mathematical characteristics, over a Hilbert space determinism implies that any possible group of systems (which are isolated from any other systems) will evolve in a single unique way from any possible initial conditions [138]; ontological determinism implies that determinism is a feature of independent reality; epistemic determinism implies that determinism is a feature of our knowledge of independent reality; see Sect.…”