Extra QLunch: Rafael Chaves

Speaker: Rafael Chaves, from the International Institute of Physics in Natal, Brazil

Title: Unveiling Quantum Signatures with Causal Interventions

Abstract: Generalizations of Bell's theorem are now being analyzed through the causal inference lens, prompting us with two new foundational inquiries. First, how interventions, a central concept in causality theory, can be integrated in Bell-like tests? Second, what is the simplest scenario leading to the incompatibility between quantum correlations and the classical theory of causality? As will be discussed, if we are not limited to observational data and can intervene in our experimental setup,  we can witness quantum violations of classical causal bounds even when no Bell-like violation is possible. Through interventions, the quantum behavior of a system, that would seem classical otherwise, can be demonstrated. Then we will present the simplest possible demonstration ofquantum nonclassicality, consisting of only three dichotomic variables, without the need for the locality assumption or external measurement choices.

References:

[1] Quantum Violation of an Instrumental Test, Nature Physics 14, 291 (2018).

[2] Quantifying causal influences in the presence of a quantum common cause. Phys. Rev. Lett. 125, 230401 (2020).

[3] Experimental test of quantum causal influences. Science Advances 8, eabm1515 (2022).

[4] Minimal Example of Quantum Nonclassicality without Freedom of Choice. Phys. Rev. Lett. 135, 090201 (2025)