  From the modern perspective of causal inference, Bell's theorem -- a
fundamental signature of quantum theory -- is a particular case where quantum
correlations are incompatible with the classical theory of causality, and the
generalization of Bell's theorem to quantum networks has led to several
breakthrough results and novel applications. Here, we consider the problem of
causal data fusion, where we piece together multiple datasets collected under
heterogeneous conditions. In particular, we show quantum experiments can
generate observational and interventional data with a non-classical signature
when pieced together that cannot be reproduced classically. We prove this
quantum non-classicality emerges from the fusion of the datasets and is present
in a plethora of scenarios, even where standard Bell non-classicality is
impossible. Furthermore, we show that non-classicality genuine to the fusion of
multiple data tables is achievable with quantum resources. Our work shows
incorporating interventions -- a central tool in causal inference -- can be a
powerful tool to detect non-classicality beyond the violation of a standard
Bell inequality. In a companion article "Quantum Non-classicality from Causal
Data Fusion", we extend our investigation considering all latent exogenous
causal structures with 3 observable variables.
