Physicists at the Large Hadron Collider (LHC) have made a groundbreaking discovery: the first observation of quantum entanglement between two quarks.
In a landmark experiment conducted at CERN, near Geneva, researchers detected a top quark, the heaviest fundamental particle, entangled with its antimatter counterpart. This marks the highest-energy detection of entanglement ever achieved and was published in the journal Nature on September 18.
The ATLAS experiment, one of the LHC's primary detectors, identified the entangled particles amidst the countless subatomic particles produced in high-energy particle collisions.
"While quantum mechanics is the foundation of particle physics, observing entanglement in a new particle system at such high energy is truly remarkable," said Andreas Hoecker, a spokesperson for ATLAS. "This opens up exciting avenues for exploring this fascinating phenomenon as we gather more data."
Entangled particles have interconnected properties. A change to one instantaneously affects the other, regardless of distance. Albert Einstein famously described this as "spooky action at a distance," but experiments have confirmed its reality.
However, many aspects of entanglement remain unexplored, especially between quarks. These subatomic particles cannot exist independently and combine to form hadrons. Baryons, like protons and neutrons, consist of three quarks, while mesons are composed of a quark and an antiquark.
Extracting individual quarks from hadrons requires significant energy, rendering them unstable and causing them to decay into jets of smaller particles.
To observe top quark entanglement, scientists at the LHC's ATLAS and CMS detectors had to identify the specific decay products of entangled particles amidst billions of others. They focused on particles whose decay products were emitted at a characteristic angle indicative of entanglement.
By carefully measuring these angles and accounting for experimental factors, the team observed top quark entanglement with sufficient statistical significance to confirm its existence. This discovery paves the way for further investigations into unknown physics.
"Studying entanglement and other quantum phenomena in a new particle system at higher energies allows us to test the Standard Model of particle physics in novel ways and search for evidence of new physics beyond it," said Patricia McBride, a spokesperson for the CMS experiment.
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Published 18 September 2024 in Nature; Observation of quantum entanglement with top quarks at the ATLAS detector; https://www.nature.com/articles/s41586-024-07824-z
