In recent years, energy-flow (light-ray) operators have emerged as a common language linking theory and experiment for mapping the dynamics of quantum field theories. In this talk, I will survey how multi-point energy correlators are used to characterize QCD matter in high-energy scattering, with emphasis on heavy ion collisions. I will review the theoretical status of light-ray correlation functions—including factorization, evolution, and medium-induced modifications—and summarize the corresponding experimental measurements. I will then argue that these observables provide controlled access to (non-vacuum) non-trivial quantum states, offering a bridge between collider phenomenology and formal developments in quantum field theory where such states remain poorly understood.
Ankita Budhraja, Phillipp Klose, Marvin Schnubel