Genuine Multipartite Nonlocality with Causal-Diagram Postselection

Year: 2021

Authors: Gebhart V., Pezzè L., Smerzi A.

Autors Affiliation: QSTAR, INO-CNR and LENS, Largo Enrico Fermi 2, Firenze, 50125, Italy; Universita, degli Studi di Napoli “”Federico II””, Via Cinthia 21, Napoli, 80126, Italy

Abstract: The generation and verification of genuine multipartite nonlocality (GMN) is of central interest for both fundamental research and quantum technological applications, such as quantum privacy. To demonstrate GMN in measurement data, the statistics are commonly postselected by neglecting undesired data. Until now, valid postselection strategies have been restricted to local postselection. A general postselection that is decided after communication between parties can mimic nonlocality, even though the complete data are local. Here, we establish conditions under which GMN is demonstrable even if observations are postselected collectively. Intriguingly, certain postselection strategies that require communication among several parties still offer a demonstration of GMN shared between all parties. The results are derived using the causal structure of the experiment and the no-signaling condition imposed by relativity. Finally, we apply our results to show that genuine three-partite nonlocality can be created with independent particle sources.


Volume: 127 (14)      Pages from: 140401-1  to: 140401-6

More Information: This work was supported by the European Commission through the H2020 QuantERA ERA-NET Cofund in Quantum Technologies project “CEBBEC.”
KeyWords: Bells-inequality; quantum; entanglrment; theorem
DOI: 10.1103/PhysRevLett.127.140401