Violation of a Bell-like inequality for spin-energy entanglement in neutron polarimetry

Violation of a Bell-like inequality for a spin-energy entangled neutron state has been demonstrated in a polarimetric experiment. The proposed inequality, in Clauser–Horne–Shimony–Holt (CHSH) formalism, relies on correlations between the spin and energy degree of freedom in a single-neutron system. The correlation function SCHSHSCHSH is determined to be 2.333±0.002⩽̸22.333±0.002⩽̸2, which violates the Bell-like CHSH inequality by more than 166 standard deviations.