2017/12/06 by Rafael Chaves, Gonzalo Carvacho, Iris Agresti +4 · 1 citation
Arts and Humanities · Computer Science · Physics and Astronomy · #Causal inference #Causal model #Causal structure #Causality (physics) #Instrumental variable #Philosophy and History of Science #Quantum #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum process #Statistical hypothesis testing #Test (biology) #quant-ph
paper · pdf · doi:10.1038/s41567-017-0008-5
published as Nature Physics 14, 291 (2018) · Main manuscript (10 pages) + Supplementary Information (8 pages)
openalex publication_date 2017/12/06 · openalex created_date 2017/12/22 · arxiv created 2018/08/29 · arxiv updated 2018/08/30 · openalex updated_date 2026/08/05
Inferring causal relations from experimental observations is of primal importance in science. Instrumental tests provide an essential tool for that aim, as they allow one to estimate causal dependencies even in the presence of unobserved common causes. In view of Bell's theorem, which implies that quantum mechanics is incompatible with our most basic notions of causality, it is of utmost importance to understand whether and how paradigmatic causal tools obtained in a classical setting can be carried over to the quantum realm. Here we show that quantum effects imply radically different predictions in the instrumental scenario. Among other results, we show that an instrumental test can be violated by entangled quantum states. Furthermore, we demonstrate such violation using a photonic set-up with active feed-forward of information, thus providing an experimental proof of this new form of non-classical behaviour. Our findings have fundamental implications in causal inference and may also lead to new applications of quantum technologies.