For the first time, we caught the heaviest particles in existence doing that 'spooky' telepathic connection thing.
March 30, 2026
Original Paper
Measurements of $Z$-boson pair entanglement in decays of Higgs bosons at the ATLAS experiment
arXiv · 2603.26463
The Takeaway
While quantum entanglement is common in tiny particles like photons, the ATLAS experiment has now proven it exists between massive Z-bosons at the electroweak scale. This confirms that quantum weirdness persists even at the extreme energies and masses found in the heart of the Large Hadron Collider.
From the abstract
Entanglement is a key property of quantum systems. In this Letter the first measurements of quantum entanglement between spins in pairs of $Z$ bosons are reported, using proton-proton collision data from the Large Hadron Collider (LHC) at center-of-mass energies of 13 TeV and 13.6 TeV, recorded with the ATLAS detector. Measurements of angular observables sensitive to $ZZ^*$ spin-density-matrix elements in the $H\rightarrow ZZ^* \rightarrow \ell^+\ell^-\ell^+\ell^-$ process yield coefficients $C_