September 25, 2024
4 min read
‘Spooky Action at a Distance’ Observed in Quarks for the First Time
Physicists report the first observations of quantum entanglement in quarks, the heaviest known fundamental particles, inside the Large Hadron Collider
The ATLAS detector, part of the Large Hadron Collider, sits 100 meters below ground, where it measures various properties of high-energy particles.
Scientists have for the first time observed quantum entanglement — a state in which particles intermingle, losing their individuality so they can no longer be described separately — between quarks. The feat, achieved at CERN, Europe’s particle-physics laboratory near Geneva, Switzerland, could open the door to further probes of quantum information in particles at high energies.
Entanglement has been measured in particles such as electrons and photons for decades, but it is a delicate phenomenon and easiest to measure in low-energy, or ‘quiet’, environments, such as in the ultracold refrigerators that house quantum computers. Particle collisions, such as those between protons at CERN’s Large Hadron Collider, are comparatively noisy and high-energy, making it much harder to measure entanglement from their debris — like listening for a whisper at a rock concert.
To observe entanglement at the LHC, physicists working on the ATLAS detector analysed about one million pairs of top and anti-top quarks — the heaviest of all known fundamental particles and their antimatter counterparts. They found statistically overwhelming evidence for entanglement, which they announced in September last year, and describe in detail today in Nature. Physicists working on the LHC’s other main detector, CMS, also confirmed the entanglement observation in a report posted to the preprint server arXiv in June.
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