Single pair measurement of CHSH by weak measurements and applications

Bell inequalities are one of the cornerstones of quantum foundations and fundamental tools for quantum tech. [1], tied to specific aspects of quantum mechanics, as quantum non-locality [2]. We present here the first single-pair Bell inequality test [3] able to obtain a Bell parameter value for every entangled pair detected. This is made possible by exploiting sequential weak measurements, allowing to perform non-commuting measurements in sequence on the same state, on each entangled particle. Such a feature grants unprecedented measurement capability. We also demonstrate how, after the Bell parameter measurement, the pair under test still presents a noteworthy amount of entanglement, providing evidence of the absence of the wave function collapse and allowing us to exploit this quantum resource for further protocols. We will discuss possible applications. [1] M.Genovese, Physics Reports 413 (2005) 319 [2] M. Genovese, M. Gramegna, Applied Science 9 (2019) 5406. [3] S.Virzì, et al. arXiv:2303.04787