Entangled in Tops: How we turned the LHC into the world’s largest quantum information experiment

A new sub-field has exploded onto the particle physics scene: testing fundamental features of quantum mechanics in collider experiments. A prominent initial result is the ATLAS Collaboration’s observation of quantum entanglement between top-quark pairs, the first measurement of entanglement between free quarks, and the highest energy lab-based quantum information experiment to date. In this talk, I will show how entanglement can be measured using a single angular observable in dileptonic top-antitop quark events, and present the measurement which led to this observation. The motivation for using the LHC as a quantum information experiment, the experimental challenges of the entanglement measurement, and the shortcomings in current modelling tools, will all be discussed. Building on the ATLAS result, I will discuss how future measurements of quantum information phenomena at the LHC may be used to set constraints on new physics, and even probe the nature of quantum theories themselves.