Atlas Technologies helps Oxford physicists track entanglement in LHC’s Z bosons

Physicists at the University of Oxford have confirmed quantum entanglement extends to some of the heaviest and most fleeting particles created at CERN’s Large Hadron Collider. The team tracked entanglement in pairs of Z bosons, particles existing for only a fraction of a second before decaying, publishing their findings in Physical Review Letters. “Quantum mechanics underpins computing and security,” explains study co-author Professor Alan Barr, Department of Physics. This demonstration bolsters the foundations of quantum physics and informs the development of technologies like quantum computing and secure communication.

Z Boson Entanglement Confirmed in LHC’s High-Energy Collisions

Tracking the decay of Z bosons produced in high-energy collisions at the Large Hadron Collider has provided direct evidence of quantum entanglement extending to comparatively massive particles. Researchers reconstructed the spin states of these fleeting bosons by meticulously analyzing the angles at which these particles were emitted, electrons and muons, detected by the ATLAS experiment. This precise reconstruction confirmed a quantum link between Z boson pairs, demonstrating entanglement isn’t limited to lighter particles like photons traditionally used in quantum experiments.

The findings, published in Physical Review Letters, expand the known boundaries of this fundamental quantum phenomenon. The ability to observe entanglement in short-lived particles challenges previous assumptions about its fragility and robustness. This has implications for quantum technologies, where maintaining entanglement is important for operations like quantum computation; the more robust entanglement proves to be, the wider the range of potential applications.

Professor Alan Barr, a co-author of the study, noted the significance of extending entanglement research to such extreme conditions, stating, “It has been gratifying to see that the use of particle colliders to test quantum effects has now become a major sub-field in physics, with more than a hundred researchers working on it worldwide.” CERN’s Quantum Technology Initiative actively supports this growing field, applying quantum computing to LHC data analysis and using its expertise in superconducting magnets for qubit development.

The LHC itself, a machine fundamentally reliant on quantum physics, continues to push the boundaries of what’s observable, while CERN partnerships with companies like IBM Quantum and Qilimanjaro Quantum Tech further accelerate the development of quantum technologies. A recent report (2026-09-13) details the construction of chips by Macquarie University for CERN’s hunt for universe origins, exemplifying this collaborative approach to advancing both fundamental physics and quantum computing capabilities.

ATLAS Detector Reconstructs Z Boson Spin via Particle Decay

The ATLAS detector at CERN precisely reconstructed the spin states of Z bosons created in high-energy collisions, confirming quantum entanglement extends to these relatively massive and short-lived particles. Researchers tracked the decay of Higgs bosons discovered in 2012, which briefly split into pairs of Z bosons before decaying further into electrons or muons, allowing for detailed analysis of the emitted particles’ angles.

This measurement builds on a 2023 experiment utilizing the same detector to demonstrate entanglement between pairs of top quarks, the heaviest known elementary particle. By reconstructing the angles at which these particles were emitted, the researchers could infer the spins of the original Z bosons and test whether they were linked by quantum entanglement.

Explained Professor Alan Barr, “Finding it alive and well among particles as heavy and short-lived as Z bosons created in some of the most violent collisions we can produce on Earth shows just how fundamental and robust this quantum effect really is.” The LHC generates these collisions by smashing protons together at 99.99% the speed of light, achieving energies of thirteen trillion electron volts.

Professor Daniela Bortoletto, UK coordinator for the upgraded ATLAS detector’s pixel system, highlighted the measurement’s significance, stating, “This measurement demonstrates the scientific power of the ATLAS collaboration and the unique capabilities of CERN’s Large Hadron Collider.” Oxford University researchers are currently involved in upgrading the ATLAS detector, a process that, combined with the High-Luminosity Large Hadron Collider will enable even more profound explorations of quantum phenomena and facilitate the application of novel quantum information techniques to the resulting massive datasets.

Project co-Principal Investigator Professor Chris Timpson (Faculty of Philosophy) added, “Entanglement is both the most promising and the most puzzling aspect of quantum reality; these collider experiments detecting entanglement present a new frontier in investigations of the foundations of quantum mechanics.

Quantum Entanglement Research Bridges Particle Physics & Computing

This extends the documented range of entanglement beyond lighter particles, suggesting the phenomenon isn’t limited to stable systems, and opens new avenues for exploring quantum mechanics at extreme energy levels. The team’s success hinges on the precision of the ATLAS detector, originally designed to reconstruct the spin of particles created in high-energy collisions and test whether they were linked by quantum entanglement.

Professor Alan Barr of Oxford’s Department of Physics, who proposed using particle colliders for entanglement research, noted the LHC’s potential extended beyond particle discovery, stating, “It’s a nice reminder that the same strange rules of quantum mechanics that may one day power quantum computers are at work everywhere in nature, even at the extreme energies of the Large Hadron Collider.” This ability to test quantum mechanics at energies trillions of times greater than previous experiments, and over distances smaller than an atomic nucleus, is a key advantage of the collider approach. This collaborative effort highlights the potential for quantum technologies to not only unlock the mysteries of the universe but also to drive advancements in computing and security.

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