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  • Open Access

Can mirror symmetry challenge local realism? Probing photon entanglement from positronium via Compton scattering

Junle Pei*

Lina Wu†

  • *Contact author: peijunle@hnas.ac.cn
  • †Contact author: wulina@xatu.edu.cn
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Phys. Rev. D 114, 073003 – Published 20 October, 2026

DOI: https://doi.org/10.1103/t6sf-gx1v

Abstract

This study investigates photon entanglement generated from parapositronium decay by analyzing azimuthal correlations after the double Compton scattering with stationary electrons. We introduce a normalized correlation observable O1=cos(2ϕ1−2ϕ2)/C1 to witness entanglement. In the absence of decoherence, ⟨O1⟩=−1, corresponding to a maximally entangled Bell state. With decoherence parametrized by ρ, the expectation becomes −(1−ρ), allowing direct experimental quantification of coherence loss. A prior symmetry analysis of the Compton scattering process within the quantum field theory (QFT) is provided, which establishes the mirror-symmetric nature of the single-photon angular distribution. We further examine a local hidden-variable theory (LHVT) under the angular-momentum conservation and the rotation invariance. Imposing the mirror symmetry with respect to the plane defined by the photon spin and momentum leads to a non-negative LHVT prediction for ⟨sin2θ1sin2θ2cos(2ϕ1−2ϕ2)⟩, contradicting the negative QFT prediction value for any ρ<1. Thus, mirror symmetry serves as a novel criterion to exclude LHVT descriptions of the entangled state, whereas without preserving this symmetry, LHVTs can reproduce the correlations.

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Phys. Rev. D 114, 073003– Published 20 October, 2026
  • Received 5 July 2026
  • Accepted 2 October 2026
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