  Quantum information observables, such as entanglement measures, provide a
powerful way to characterize the properties of quantum states. We propose to
use them to probe the structure of fundamental interactions and to search for
new physics at high energy. Inspired by recent proposals to measure
entanglement of top quark pairs produced at the LHC, we examine how
higher-dimensional operators in the framework of the SMEFT modify the Standard
Model expectations. We explore two regions of interest in the phase space where
the Standard Model produces maximally entangled states: at threshold and in the
high-energy limit. We unveil a non-trivial pattern of effects, which depend on
the initial state partons, $q\bar q$ or $gg$, on whether only linear or up to
quadratic SMEFT contributions are included, and on the phase space region. In
general, we find that higher-dimensional effects lower the entanglement
predicted in the Standard Model.
