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arXiv:2510.09466 · Physical Review C

Entanglement and accidental symmetries in the nucleon-nucleon system

Alma L. Cavallin, Oliver Thim, C. Forssén

Published Jan 8, 2026• 5 citations
arXivHTMLPDF

Abstract

We study the connection between accidental symmetries in the nuclear interaction and spin entanglement in two-nucleon scattering. Specifically, we incorporate different levels of Wigner SU(4) and Serber symmetries into leading-order potentials derived from chiral effective field theory. We conduct a quantitative analysis by computing the full S matrix, demonstrating that the neutron-proton spin entanglement can be related to the symmetry properties of the interaction and the presence of certain operators and partial waves. Furthermore, we study the order-by-order evolution of the spin entanglement, up to next-to-next-to-leading order in Weinberg power counting, for both neutron-proton and neutron-neutron scattering. Entanglement suppression is not observed in neutron-neutron scattering, which can be attributed to the Pauli principle and the absence of accidental symmetries in this system. We conclude that entanglement is a useful guide for studying the power counting and symmetries in nuclear interactions derived from effective field theories.

DOI
10.1103/mlt1-z7t2

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Nucleon-nucleon scattering is a fundamental process in low-energy nuclear physics. Although its spin correlations have been studied intensively, few works take the perspective of quantum information science. In this work, I explore the quantum information aspects of spin correlations in the partially polarized neutron-proton scattering in the SSS wave. It is found that the spin mutual information, entanglement and discord of the out-states, when averaged over the possible in-states, all vary in a similar way with respect to the relative momentum. The novel connection between emergent symmetry and spin entanglement found by a previous study [Phys. Rev. Lett. 122, 102001 (2019)] could then be extended naturally to spin correlations beyond entanglement.
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