Quantum tomography beyond the leading order

Quantum tomography, as a tool to probe foundational aspects of quantum mechanics, relies on extracting spin information from angular distributions. This is inherently a leading-order technique, ill-defined when higher-order corrections are significant. For those cases, we propose to treat higher-order corrections as a background, to be modeled and subtracted from data in the same way as other backgrounds are. We illustrate this procedure for Higgs decays $H \to ZZ \to e^+ e^- \mu^+ \mu^-$, which is of high interest for upcoming qutrit entanglement tests at the Large Hadron Collider.