Λ-hyperon spin correlations as a probe of Bell-type inequalities and quantum entanglement at high energy colliders

The spin correlations of Λ-hyperons, due to their self-analyzing property in weak decays, can provide unique insight into Bell-type locality tests within the QCD strings formed in experiments at high-energy colliders-- specifically, tests of the CHSH (Clauser-Horne-Shimony-Holt) inequality. We show, from very general considerations, that the CHSH inequality test is typically less stringent for the states produced in QCD strings; however, they can be used to study quantum-to-classical transitions by varying control parameters such as i) the number of partons, or equivalently, the multiplicity of a string, ii) the spin of nucleons, and iii) the separation in rapidity between pairs. These measurements also allow, as a function of the stated control parameters, the extraction of quantitative measures of entanglement, the most straightforward being the entanglement fidelity of Λ Λ-bar spin correlations. We discuss a class of spin Hamiltonians that captures the dynamics of such spin correlations within the QCD string and outline the requirements for their simulation on a quantum computer. We further discuss the prospects for such measurements at current and future colliders.