Physicists at the Large Hadron Collider (LHC) near Geneva have detected quantum entanglement for the first time between two unusually heavy, extremely short-lived Z bosons produced in the decay of a Higgs boson. The phenomenon Albert Einstein once dismissed as “spooky action at a distance” has now been shown to survive even among the most fleeting particles in high-energy physics.
Entanglement from a Higgs decay
The team, part of the ATLAS collaboration at CERN and including the University of Oxford, analysed collisions at roughly 13 trillion electronvolts. In these events a Higgs boson briefly splits into a pair of Z bosons, which almost instantly decay into electrons or muons. By reconstructing the emission angles of those measurable particles, the researchers inferred the spins of the original Z bosons and tested whether they were quantum-mechanically linked.
A robust 4.7-sigma result
The evidence is statistically solid: a test using the full angular distribution disfavoured the hypothesis of separable, non-entangled particles at a significance of 4.7 standard deviations relative to the entangled Standard Model prediction. That makes it one of the highest-energy confirmations of entanglement on record. Earlier LHC measurements found the effect in top quarks; seeing it in such heavy, unstable bosons underscores, the team says, how fundamental and robust the effect really is.
Why it matters beyond particle physics
Entanglement underpins quantum computing and tap-proof communication. Confirming it under the universe’s most extreme conditions supports the view that quantum mechanics holds even at the highest energies. This is a real experimental measurement, not a simulation or pure theory.
Source: ATLAS collaboration (CERN) and the University of Oxford, published in Physical Review Letters on 11 September 2026: “Measurements of Z-Boson Pair Entanglement in Decays of Higgs Bosons at the ATLAS Experiment,” DOI 10.1103/y1nh-1b82.
