Nonmaximal entanglement of photons from positron-electron annihilation demonstrated using a plastic PET scanner

• DOI: 10.1126/sciadv.ads3046
• Publication Date: 2025-05-01T02:03:58Z
• Authors: Paweł Moskal; Deepak Kumar; Sushil Sharma; Ermias Yitayew Be...; Neha Chug; Aurélien Coussat; Catalina Curceanu; Eryk Czerwiński; Manish Das; Kamil Dulski; Marek Gorgol; Bożena Jasińska; Krzysztof Kacprzak; Tevfik Kaplanoglu; Łukasz Kapłon; Tomasz Kozik; Edward Lisowski; Filip Lisowski; Wiktor Mryka; Szymon Niedźwiecki; Szymon Parzych; Elena P. del Rio; Martin Rädler; Magdalena Skurzok; Ewa Ł. Stepień; Pooja Tanty; Keyvan Tayefi Ard...; Kavya Valsan Eliyan

In state-of-the-art positron emission tomography (PET), information about annihilation photon polarization is unavailable. Here, we present a PET scanner built from plastic scintillators, where annihilation photons primarily interact via the Compton effect, providing information about both photon polarization and propagation direction. Using this plastic-based PET, we determined the distribution of the relative angle between polarization planes of photons from positron-electron annihilation in a porous polymer. The amplitude of the observed distribution is smaller than predicted for maximally quantum entangled two-photon states but larger than expected for separable photons. This result can be well explained by assuming that photons from pick-off annihilation are not entangled, while photons from direct and parapositronium annihilations are maximally entangled. Our result indicates that the degree of entanglement depends on the annihilation mechanism in matter, opening avenues for exploring polarization correlations in PET as a diagnostic indicator.