Researchers find a brand-new kind of quantum entanglement.

 By Michael Irving

Jan 5, 2023

The eerie phenomenon known as quantum entanglement, which bonds particles over any distance, has been entirely new form of entanglement found by physicists at Brookhaven National Laboratory (BNL). The new entanglement made it possible for researchers to take a closer-than-ever look into atomic nuclei during particle collider tests.

No matter how far apart they may be, pairs of particles can intertwine to the point where one can no longer be represented without the other. Stranger still, altering one will immediately cause its partner to alter, even if the partner is on the other side of the universe. We are rooted in the world of conventional physics, therefore the concept of quantum entanglement seems inconceivable to us. It frightened even Einstein, who described it as "spooky action at a distance." However, it has been continually supported by decades of tests, and it serves as the foundation for cutting-edge technology like quantum networks and computers.

Typically, quantum entanglement is observed between identically-natured pairs of photons or electrons. But now, the BNL team has discovered pairs of disparate particles engaging in quantum entanglement for the first time.

The finding was made in the Brookhaven Laboratory Relativistic Heavy Ion Collider (RHIC), which accelerates and collides gold ions to study the composition of matter in the early cosmos. The scientists discovered, however, that there is plenty to be learned from near misses even when the ions do not collide.

The photons that surround the accelerated gold ions may more clearly than ever before capture an image of the other ion's interior structure when two ions are passing near to one another. The scientists find it fascinating enough on its own, but it is possible only because of a novel type of quantum entanglement.

In each ion's nucleus, elementary particles interact with the photons, starting a chain reaction that finally results in two pairs of particles termed pions, one positive and one negative. Some particles, as you may recall from high school physics, can also be thought of as waves. In this instance, the waves from the two positive and negative pions reinforce one another. As a consequence, the detector is only hit by one positive and one negative pion wave function.

This shows that every pair of positive and negative pions is intertwined. The team asserts that if they weren't, the wave functions that hit the detector would be totally arbitrary. As a result, this is the first time that different particle quantum entanglement has been discovered.

According to Zhangbu Xu, one of the study's authors, "we measure two outgoing particles and clearly their charges are different—they are different particles—but we see interference patterns that indicate these particles are entangled, or in sync with one another, even though they are distinguishable particles."

The finding might result in new technologies, such as the approach the team has been employing to see into the nucleus of the gold ions, in addition to advancing our knowledge of quantum mechanics.