Toponium effects on quantum steering and Bell nonlocality of top quarks

We investigate quantum steering and Bell nonlocality in top-quark pair production at the LHC near threshold. The toponium contribution strengthens the spin-singlet component and substantially enhances the entanglement between the two quark spins. With current LHC data, quantum steering appears observable with a statistical significance around $10σ$. For Bell nonlocality, the statistical significance can also be high close to threshold, reaching about $9σ$, although the feasibility of such a measurement will depend crucially on the control of systematic uncertainties.