Researchers using the ATLAS experiment at CERN’s Large Hadron Collider have confirmed quantum entanglement between pairs of short-lived Z bosons at energies reaching thirteen trillion electron volts, according to a study published in Physical Review Letters. By tracking electrons and muons, the team inferred the spins of the fleeting particles to record one of the highest-energy confirmations of the phenomenon to date.
Tracking Z Bosons at CERN
Physicists examined Z bosons that exist for only a fraction of a second before decaying. According to the ATLAS collaboration, these particles were produced when Higgs bosons split during proton-proton collisions traveling at 99.99% the speed of light near Geneva, Switzerland. Although the Z bosons vanished almost instantly, the ATLAS detector precisely tracked the resulting electrons and muons. By analyzing the angles of these decay products, scientists inferred the original spins of the Z bosons to test for entanglement.
Did you know? Albert Einstein famously referred to quantum entanglement as “spooky action at a distance.” While historically demonstrated in systems like photons and trapped ions, this recent CERN measurement proves the effect survives extreme, violent particle collisions.
Building on Prior Top Quark Findings
This measurement follows a 2023 experiment using the ATLAS detector that demonstrated entanglement between pairs of top quarks, which are the heaviest known elementary particles. Professor Alan Barr from the Department of Physics at Oxford University was one of the first to propose using particle colliders to investigate quantum entanglement at vastly higher energy levels than previous laboratory tests. According to Professor Barr, finding entanglement among particles as heavy as Z bosons shows just how fundamental and robust the quantum effect is in nature.
Oxford researchers are also involved in upgrades to the ATLAS detector and the High-Luminosity Large Hadron Collider. According to Professor Daniela Bortoletto from Oxford’s Department of Physics, these enhancements will allow teams to apply novel quantum information techniques to even larger data sets.
Philosophical and Technological Implications
Beyond confirming standard model predictions, these high-energy measurements connect directly to foundational questions in physics. At Oxford University, Professor Barr and Professor Chris Timpson from the Faculty of Philosophy co-lead an interdisciplinary project exploring the foundations of quantum mechanics at high energies. According to Professor Timpson, collider experiments detecting entanglement present a new frontier in investigating quantum reality.
While lab-scale entanglement underpins emerging technologies like quantum computers and ultra-secure communication networks, high-energy confirmations help researchers understand whether these rules hold firm under extreme physical conditions. These methods could eventually support more sensitive ways to analyze massive volumes of particle-collider data.
Frequently Asked Questions
What is quantum entanglement?
Quantum entanglement occurs when two particles share an origin and remain connected so that measuring a property of one instantly reveals information about its partner, regardless of distance.
How did researchers detect entanglement in Z bosons?
According to the ATLAS collaboration, researchers inferred the spins of the short-lived Z bosons by analyzing the precise angles of the electrons and muons produced when the bosons decayed.
What energy levels were involved in the CERN experiment?
The Higgs bosons producing the Z bosons were generated by smashing protons together at 13 trillion electron volts.
Who published the study?
The study, titled “Measurements of Z-boson pair entanglement in decays of Higgs bosons at the ATLAS experiment,” was published in Physical Review Letters by researchers working with CERN’s Large Hadron Collider.
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