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An experiment by a group of physicists led by University of Rochester physics professor Regina Demina has produced a significant result related to quantum entanglement, an effect Albert Einstein called “spooky action at a distance.”

Entanglement refers to the coordinated behavior of tiny particles that have interacted but then drifted apart. Measuring properties—such as position, momentum, or spin—of one of the separated pair of particles immediately changes the results of the other particle, no matter how far the second particle has moved from its twin. In fact, the state of one entangled particle or qubit is inseparable from the other.

Quantum entanglement has been observed between stable particles such as photons or electrons.

But Demina and her group broke new ground as they discovered for the first time that entanglement persists between unstable top quarks and their antimatter partners at distances beyond what can be covered by information transferred at the speed of light. Specifically, the researchers observed spin correlation between the particles.

The particles therefore demonstrated what Einstein described as “spooky action at a distance.”

A ‘new path’ for quantum research

The finding was reported by the Compact Muon Solenoid (CMS) Collaboration at the European Center for Nuclear Research, or CERN, where the experiment was conducted.

“The confirmation of quantum entanglement between the heaviest fundamental particles, the top quarks, has opened a new avenue for probing the quantum nature of our world at energies far beyond what is accessible,” the report said.

CERN, located near Geneva, Switzerland, is the world’s largest particle physics laboratory. Producing top quarks requires the very high energies available at the Large Hadron Collider (LHC), which allows scientists to send high-energy particles spinning around a 17-kilometer underground track at speeds close to the speed of light.

The phenomenon of entanglement has become the basis of a burgeoning field of quantum information science, which has broad implications in areas such as cryptography and quantum computing.

Top quarks, each as heavy as a gold atom, can only be produced in colliders such as the LHC, and thus are unlikely to be used to build a quantum computer. But studies like those conducted by Demina and her group can shed light on how long the entanglement lasts, whether it is passed on to the particle’s “daughters” or decay products, and what, if anything, ultimately breaks the entanglement.

Theorists believe that the universe was in a entangled state after the initial stage of rapid expansion. The new result observed by Demina and her researchers may help scientists understand what caused the loss of quantum coupling in our world.

Top quarks in long-range quantum entanglements

Demina recorded a video for CMS’ social media channels to explain the result to her group. She used the analogy of an indecisive king from a distant land whom she called “King Top”.

King Top receives word that his country is under attack, so he sends messengers to tell all the people in his land to prepare for defense. But then, Demina explains in the video, he changed his mind and sent messengers to order the people to retreat.

“He keeps spinning like this, and nobody knows what his decision will be in the next moment,” says Demina.

No one, Demina explains, except the leader of a village in this kingdom, who is known as “Anti-Top.”

“They know their state of mind at any given moment,” says Demina.

Demina’s research group consists of her and graduate student Alan Herrera and postdoctoral fellow Otto Hindrichs.

As a graduate student, Demina was on the team that discovered the top quark in 1995. Later, as a faculty member at Rochester, Demina led a team of scientists from across the US who built a tracking device that played a key role in the 2012 discovery d. of the Higgs boson – an elementary particle that helps explain the origin of mass in the universe.

Rochester researchers have a long history at CERN as part of the CMS Collaboration, which brings together physicists from around the world. Recently, another Rochester team achieved an important milestone in measuring the electroweak mixing angle, a crucial component of the Standard Model of particle physics that explains how the building blocks of matter interact.