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arXiv:2501.09874

Phase-Shifted Bell States

J. J. Joshua Davis, Carey L. Jackman, R. Leonhardt, Paul J. Werbos, Maarten D. Hoogerland

Published Jan 16, 2025• 0 citations
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Abstract

Inspired by previous studies and pioneers of the field, we present new results on an extensive EPR-Bell experiment using photons generated by parametric down conversion, where one of the photons is deliberately phase-shifted. Our experiments show some surprising results for particular angles of this phase shift.
DOI
10.48550/arxiv.2501.09874

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Inspired by previous studies and pioneers of the field, we present new results on an extensive Einstein, Podolsky, and Rosen (EPR)–Bell experiment using photons generated by parametric down-conversion, where one of the photons is deliberately phase-shifted. Our experiments show some surprising results for particular angles of this phase shift, where, for some states, the Clauser, Horne, Shimony, and Holt inequality shows no violations, requiring us to review our understanding of “entangled” states vis-à-vis the correlations obtained via experimental coincidence counts in agreement with quantum mechanics theoretical predictions. We give some possible explanations about the correlated states that show no violations of these inequalities.
This paper conveys briefly and concisely what could be the implications of the Einstein-Bohr debate when we consider the results of Phase-Shifted EPR-Bell states from a study conducted in Maarten Hoogerland’s Lab in the Dodd-Walls Centre for Photonics and Quantum Technologies, University of Auckland, New Zealand (2018-2024). The results of this study were presented at the first Biological Physics and Meaning Mini Conference on ‘QUANTUM MECHANICS, THE MEASUREMENT PROBLEM AND HUMAN CONSCIOUSNESS’ (Feb. 2024). Here, I also examine the nature of correlated pairs of photons produced by Spontaneous Parametric Down Conversion (SPDC) Type II, when the photon of one path is altered with a Quarter Wave Plate (QWP), shifting the polarization from linear to elliptical or circular. As stated in the above mentioned study, surprisingly, some of these Phase Shifted Bell states (correlated pairs) produce no violation of the Clauser, Horne, Shimony and Holt (CHSH) inequality, raising yet again a question mark on the meaning of ‘entanglement’ when understood as ‘spooky action at a distance’, in the context of the formalism of Quantum Mechanics and the different associated interpretations. If ‘spooky action at a distance’ is ruled out from physical systems and we consider new more general stochastic laws, then we open the way for a more interesting future physics on the side of Einstein and realism that, under some regimes, may manifest as nonlocality in terms of information structures. Perhaps, religious, spiritual and mystical experience (RSME) may have a place in physics and the sciences in general, as experienced information and meaning within physical restrictions in a classically consciously experienced lived life in spacetime.
Interwoven frustrated parametric down-conversion (PDC) processes produce interference effects based on path identity [Krenn et al., Entanglement by path identity, Phys. Rev. Lett. 118, 080401 (2017)PRLTAO0031-900710.1103/PhysRevLett.118.080401]. In this Letter we show Bell nonclassicality of the processes: a proper violation of the Clauser-Horne inequality when the local measurements are controlled by on-off switching of the final local PDC processes. Such a nonstandard approach is needed because if only the local phase shifts are used for the measurement settings, as done in the experiment reported in Wang et al. [Violation of Bell inequality with unentangled photons, Sci. Adv. 11, eadr1794 (2025)SACDAF2375-254810.1126/sciadv.adr1794], there exists a local realistic model of the interference, which we present in this Letter. Nevertheless, the reported destructive interference is deep enough to violate the inequality when using on-off switching, so our result establishes a firm footing for nonclassicality of the new interferometry, in both theory and experiment. The on-off approach to Bell analysis of path-identity-based interference forms a new platform for seeking new highly counterintuitive quantum phenomena.