CERN Accelerating science
At CERN, we probe the fundamental structure of particles that make up everything around us. We do so using the world's largest and most complex scientific instruments.
Quantum entanglement is a fascinating feature of quantum physics – the theory of the very small. If two particles are quantum-entangled, the state of one particle is tied to that of the other, no matter how far apart the particles are. This mind-bending phenomenon, which has no analogue in classical physics, has been observed in a wide variety of systems and has found several important applications, such as quantum cryptography and quantum computing. In 2022, the Nobel Prize in Physics was awarded to Alain Aspect, John F. Clauser and Anton Zeilinger for groundbreaking experiments with entangled photons. These experiments confirmed the predictions for the manifestation of entanglement made by the late CERN theorist John Bell and pioneered quantum information science.
Entanglement has remained largely unexplored at the high energies accessible at particle colliders such as the Large Hadron Collider (LHC). In an article published today in Nature, the ATLAS collaboration reports how it succeeded in observing quantum entanglement at the LHC for the first time, between fundamental particles called top quarks and at the highest energies yet. First reported by ATLAS in September 2023 and since confirmed by a first and a second observation made by the CMS collaboration, this result has opened up a new perspective on the complex world of quantum physics.
