A quantum experiment with joint exogeneity violation

Abstract

In randomized experiments, the assumption of potential outcomes is usually accompanied by the \emph{joint exogeneity} assumption. Although joint exogeneity has faced criticism as a counterfactual assumption since its proposal, no evidence has yet demonstrated its violation in randomized experiments. In this paper, we reveal such a violation in a quantum experiment, thereby falsifying this assumption, at least in regimes where classical physics cannot provide a complete description. We further discuss its implications for potential outcome modelling, from both practial and philosophical perspectives.

This is a preliminary draft in accordance to the presentations of YW at the 2025 Pacific Causal Inference Conference and 2025 Chinese Causal Inference Conference. This draft is being circulated to collect further feedback. A formal version will be publicly available in due course