An experiment led by University of Rochester physics professor Regina Demina has produced a significant result related to quantum entanglement—an effect famously dubbed “spooky action at a distance” by Albert Einstein. Entanglement refers to the interconnected behavior of particles that, after interacting, remain linked regardless of the distance separating them. When the properties of one particle are measured, the results instantaneously influence its entangled partner.
Previously, entanglement was observed among stable particles like photons or electrons. However, Demina’s group has broken new ground by demonstrating that entanglement persists between unstable top quarks and their antimatter partners at distances greater than what can be traversed by light. The researchers specifically observed spin correlation between these particles, confirming Einstein’s “spooky action at a distance.”
This breakthrough was reported by the Compact Muon Solenoid (CMS) Collaboration at CERN, where the experiment took place. The confirmation of quantum entanglement between top quarks, the heaviest known fundamental particles, opens a new avenue for exploring quantum phenomena at high energies.
CERN, located near Geneva, Switzerland, is the world’s largest particle physics laboratory. Top quarks, which are as heavy as an atom of gold, require the high energies produced by the Large Hadron Collider (LHC) to be created. The LHC accelerates particles around a 17-mile underground track at nearly the speed of light.
While top quarks are unlikely to be used in quantum computing due to their instability, studies like Demina’s can illuminate how long entanglement persists and whether it is passed on to decay products. This research may also help scientists understand the loss of quantum entanglement in the universe’s early history.
Professor Demina used a creative analogy to explain the concept: she likened the entanglement to a king named “King Top,” who frequently changes his decisions about an invasion. Only “Anti-Top,” the leader of a distant village, knows the king’s state of mind at any given moment.
Demina’s team includes graduate student Alan Herrera and postdoctoral fellow Otto Hindrichs. Demina was part of the team that discovered the top quark in 1995 and later co-led a team that played a key role in the discovery of the Higgs boson in 2012. The Rochester research team has a long history of contributions to the CMS Collaboration at CERN.
