Extending the fair sampling assumption using causal diagrams

Year: 2023

Authors: Gebhart Valentin; Smerzi Augusto

Autors Affiliation: QSTAR, INO-CNR and LENS, Largo Enrico Fermi 2, 50125 Firenze, Italy

Abstract: Discarding undesirable measurement results in Bell experiments opens the detection loop-hole that prevents a conclusive demonstration of nonlocality. As closing the detection loop-hole represents a major technical challenge for many practical Bell experiments, it is customary to assume the so-called fair sampling assumption (FSA) that, in its original form, states that the collectively postselected statistics are a fair sample of the ideal statistics. Here, we analyze the FSA from the viewpoint of causal inference: We derive a causal structure that must be present in any causal model that faithfully encapsulates the FSA. This provides an easy, intuitive, and unifying approach that includes different accepted forms of the FSA and underlines what is really assumed when using the FSA. We then show that the FSA can not only be applied in scenarios with non-ideal detectors or transmission losses, but also in ideal experiments where only parts of the correlations are postselected, e.g., when the particles? destinations are in a superposition state. Finally, we demonstrate that the FSA is also applicable in multipartite scenarios that test for (genuine) multipartite nonlocality.

Journal/Review: QUANTUM

Volume: 7      Pages from: 897-1  to: 897-10

More Information: This work was supported by the European Commission through the H2020 QuantERA ERA-NET Co-fund in Quantum Technologies project “”MENTA””.
DOI: 10.22331/q-2023-01-13-897