Researchers at the ATLAS experiment have detected quantum entanglement between Z-boson pairs, proving that Einstein’s ‘spooky action’ persists even in the high-energy environment of the Large Hadron Collider.
A fundamental pillar of quantum mechanics has passed a rigorous new test at the world’s most powerful particle accelerator. Researchers utilizing the ATLAS experiment at the Large Hadron Collider (LHC) near Geneva have reported the first measurement of quantum entanglement between pairs of Z bosons. The findings, published in Physical Review Letters on September 11, 2026, demonstrate that the phenomenon Albert Einstein famously dismissed as “spooky action at a distance” persists even among some of the heaviest and most fleeting particles in existence.
Quantum entanglement occurs when two particles become so inextricably linked that the state of one cannot be described independently of the other, regardless of the distance between them. While this effect has been observed in stable particles like photons, electrons, and trapped ions, testing it in the violent, high-energy environment of a particle collider presents unique challenges. The Z bosons studied in this experiment exist for only a tiny fraction of a second before decaying, making them difficult subjects for traditional quantum observation.
The international team, including significant contributions from the University of Oxford, analyzed proton-proton collision data at center-of-mass energies of 13 and 13.6 TeV. They focused on a specific decay channel where a Higgs boson—the particle responsible for giving other particles mass—decays into two Z bosons, which subsequently decay into four charged leptons, specifically electrons or muons. By measuring the specific angles at which these particles emerged, the team reconstructed the spin-density-matrix coefficients of the original Z bosons, reporting values of C = -0.71 ± 0.45 for the primary correlation coefficient.
The results disfavored a non-entangled, separable state at a statistical significance of 4.7 standard deviations, coming remarkably close to the expected sensitivity of 4.9. While the collaboration noted that this is not a direct observation of separated particles communicating faster than light, nor a reported Bell-inequality violation, it serves as high-energy evidence for entanglement inferred from decay-angle correlations. This measurement follows a 2023 ATLAS experiment that demonstrated entanglement in top quarks, further proving that the rules of quantum information science apply to the heaviest building blocks of the Standard Model.
Professor Alan Barr of Oxford’s Department of Physics, a study co-author who has long advocated for using colliders as high-energy quantum laboratories, noted that finding entanglement in such short-lived particles shows the robustness of the effect. Barr, who was involved in building the LHC, recognized that the enormous collider could serve purposes beyond the search for new particles. The work suggests that the same principles currently being harnessed to develop quantum computers and ultra-secure communication networks are fundamental to the behavior of nature at its most extreme scales, even when particles are moving at 99.99% the speed of light.
This research is part of a broader interdisciplinary effort to bring concepts from quantum information science into high-energy particle physics. By applying ideas developed for quantum systems to the enormous data sets produced by particle colliders, researchers hope to create more sensitive ways of detecting subtle patterns. These techniques could eventually reveal effects that do not fit within physicists’ current understanding of the universe and potentially offer clues about physics beyond existing theories, such as dark matter or the unification of forces.
Looking forward, the integration of quantum information techniques into high-energy physics may provide new methods for detecting patterns that deviate from the Standard Model. As CERN prepares for the High-Luminosity LHC upgrade, the resulting increase in data will allow for even more precise tests of quantum foundations. Oxford researchers are already contributing to the upgrade of the ATLAS detector’s pixel system to handle these larger data sets. These experiments not only validate existing theories but also push the boundaries of international scientific cooperation in the quest to understand the underlying nature of reality and the sovereignty of physical laws.
Mason Reed serves as a Staff Writer for Just Right News, where he spearheads the Future Frontiers & Special Projects desk. In an era defined by rapid technological shifts and evolving social landscapes, Mason provides a steady, principled voice, examining the innovations of tomorrow through the lens of traditional American values. His work is most prominently featured in his signature series, “The Next Horizon,” where he explores the intersection of emerging technology, national sovereignty, and the preservation of individual liberty.
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