EPJ Plus Highlight - Probing quantum weirdness using particle colliders

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Published on 21 October 2025

An international collaboration of researchers presents a roadmap of future experiments at colliders like the LHC, investigating the nature of quantum correlations, such as entanglement and Bell nonlocality at ultra-high energies

So far, many of the most mind-bending properties of quantum mechanics have only been studied extensively in low-energy laboratory setups. Recently, however, researchers have begun to consider how these experiments could be carried out at higher energies – achievable through particle accelerators like the Large Hadron Collider (LHC). Offering energies some 12 orders of magnitude higher than lab setups, these instruments provide a novel environment where quantum phenomena can be probed experimentally.

Through a new paper published in EPJ Plus, an international collaboration of researchers presents a roadmap for these studies: identifying the challenges that need to be overcome, and setting out realistic goals for future research, which may be carried out in different scenarios at future generations of colliders. The team’s analysis could help guide efforts to deepen our understanding of the enigmatic nature of quantum mechanics.

Many quantum systems are made up of multiple subsystems, which may be interconnected via entanglement – a uniquely quantum correlation that can persist even when the subsystems are separated. When entanglement is present, the system cannot be described from its individual parts. In some cases, these correlations exhibit Bell nonlocality, meaning they are strong enough to violate a Bell inequality – a test originally formulated to probe whether quantum mechanics provides a complete description of reality. While both entanglement and Bell nonlocality are central to quantum theory, they haven’t yet been widely investigated at the higher energies offered by collider experiments like the LHC.

Since the detectors at these facilities were not originally designed for such measurements, studying quantum correlations is challenging, but not impossible. Recently, the ATLAS and CMS collaborations have measured entanglement between the spins of top quark–antiquark pairs, while many phenomenological studies have demonstrated the potential to measure entanglement and Bell nonlocality in other exotic particles produced through high-energy collisions. One of the key features of these results is the use of quantum tomography techniques, which connect the spin of parent particles, such as the top quark, to the directions and energies of the final-state particles measured at collider experiments.

Through these early results, a dedicated scientific community has been forming, bringing together researchers from both experimental and theoretical backgrounds, and from the high-energy physics, quantum information, and quantum computing communities. By elaborating on the goals and potential challenges of this innovative, rapidly evolving line of research, the scientific community clearly shows how these studies are paving the way for a new generation of high-energy measurements.