Suffolk Reporter

Geneva, 18 September 2024. Quantum entanglement, a phenomenon where the state of one particle is tied to that of another regardless of distance, has been observed at unprecedented energy levels at CERN’s Large Hadron Collider (LHC). This observation was made by the ATLAS collaboration and published in Nature.

The Nobel Prize in Physics in 2022 was awarded to Alain Aspect, John F. Clauser, and Anton Zeilinger for their experiments with entangled photons, confirming predictions by the late CERN theorist John Bell. These groundbreaking experiments have significantly advanced quantum information science.

Until now, quantum entanglement had not been extensively studied at the high energies accessible at particle colliders like the LHC. The ATLAS collaboration reports observing quantum entanglement between fundamental particles called top quarks at the highest energies yet recorded. This result, first reported by ATLAS in September 2023 and later confirmed by two observations from the CMS collaboration, introduces new perspectives on quantum physics.

"While particle physics is deeply rooted in quantum mechanics, the observation of quantum entanglement in a new particle system and at much higher energy than previously possible is remarkable," said ATLAS spokesperson Andreas Hoecker. "It paves the way for new investigations into this fascinating phenomenon, opening up a rich menu of exploration as our data samples continue to grow."

The teams from ATLAS and CMS focused on pairs of top quarks produced during proton-proton collisions at an energy of 13 teraelectronvolts between 2015 and 2018. They particularly examined pairs produced with low relative momentum where strong spin entanglement was expected.

Top quarks are the heaviest known fundamental particles and decay quickly into other particles, transferring their spin traits to these decay products. By measuring the angular separations between electrically charged decay products and correcting for experimental effects, both teams observed spin entanglement between top quarks with statistical significance exceeding five standard deviations.