Quantum Mechanics is the fundamental theory of the microscopic world, developed at the beginning of the 20th century. The study of quantum foundations and the classical-quantum frontier is still nowadays an active field of research, with direct applications in quantum technologies. However, little attention has been devoted to experimental tests of quantum signatures at relativistic energies, even though it is a subject of fundamental interest. We discuss how high-energy colliders can become a unique laboratory for such purposes. We focus on the paradigmatic case of a top-antitop quark pair, a drosophila of relativistic two-qubit system, since its quantum state can be fully reconstructed from the angular distribution of the decay products. We discuss how quantum correlations, such as entanglement, can be studied in high-energy colliders using top-quark pairs, including recent measurements by ATLAS and CMS. Finally, we outline future avenues for the development of the exciting field of quantum colliders.
Joachim Kopp