Informational Pruning as a Third Path: Final-State Constraints between Consistent Quantum Causes and Quantum Causal Models
Author
Ian Staley
Abstract
Two recent programs offer competing accounts of quantum causation. Griffiths' Consistent Quantum Causes grounds causal reasoning in the Consistent Histories formalism, treating stochastic time development and noncommuting projectors as the foundation for a Pearl-style causal graph. The Costa and Shrapnel Quantum Causal Models program takes the process-matrix formalism as its starting point and extends naturally to indefinite causal order. Both assume causal structure is fixed by an initial condition and forward dynamics, and neither addresses admissibility conditioned at both temporal boundaries. This paper argues that final-state-constrained history ensembles, and the informational pruning they induce, provide a third vantage point on the two programs. The claim is not that the disagreement is resolved, but that once admissibility is globally filtered by an initial and a final boundary condition, the question of which coarse-grained histories carry the effective causal structure of the process is reframed. The Hartle and Craig rank-product theorem supplies the formal backbone, and the three-box paradox provides a worked illustration in which the filter reduces two framework choices to one admissible history each and excludes the third. An explainability stance, drawn methodologically from explainable artificial intelligence, sharpens which admissible histories do the explanatory work.
Keywords
Consistent histories; quantum causal models; final boundary condition; informational pruning; rank-product theorem; three-box paradox
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References
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