Understanding quantum entanglement in nuclear processes requires elucidating how coherence lengths govern quantum correlations—a critical challenge at the intersection of nuclear physics and quantum information science. This work demonstrates that radiative capture reactions exhibit three distinct regimes dictated by the coherence length Lc: preservation of spin-photon entanglement at long Lc (> 10−17 cm), characterized by anisotropic γ -ray emission (a2 > 0.5) and vanishing entropy (S < 0.1); complete decoherence at short Lc (< 10−20 cm), producing isotropic radiation (a2 ∼ 0) and maximal entropy (S → 1); and intermediate polarization correlations (ξ ∼ 0.2) in mixed multipole transitions, where partial decoherence (S ∼ 0.5) reveals residual phase stability. The universal scaling Lc c/ directly ties these regimes to the reaction’s decay width , enabling predictive control over entanglement dynamics. Long-Lc systems, such as 6Li(n, γ ) 7Li, emerge as natural entanglement sources for quantum sensing and tests of nonlocality, while short-Lc regimes refine models of nucleosynthesis in stellar environments.
