Nuclear physicists have used a type of quantum entanglement never seen before to help them obtain information about the interior of an atomic nucleus.
At the Relativistic Heavy Ion Collider (RHIC) – a particle collider at the US Department of Energy’s Brookhaven laboratory in the United States – physicists were able to use the photons (particles of light) surrounding gold ions passing through the collider to observe the structure of the atom. nuclei and pairs of entangled particles.
Called “frightening action at a distance” by Einstein, quantum entanglement connects the physical states of particles, regardless of their distance. Until now, quantum entanglement has only been observed between particles of the same type, for example entangled pairs of electrons or photons.
In their experiment, the nuclear physicists observed photons interacting through a series of quantum fluctuations with gluons in gold ions, traversing the RHIC. Imaginatively named, gluons are – wait for it – glue-like particles responsible for the strong force that holds quarks together – which in turn form the protons and neutrons in atomic nuclei.
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A new intermediate particle is produced by the interaction between photons and gluons. This particle rapidly decays into oppositely charged particles called “pions” (denoted by the Greek letter π). The speed and trajectory of the π+ and π– can be used to gain crucial photon information and determine the arrangement of gluons in the nucleus more accurately than ever before.
“This technique is similar to how doctors use positron emission tomography (PET) to see what’s going on inside the brain and other parts of the body,” says the former Brookhaven Lab physicist. , James Daniel Brandenburg, now an assistant professor at Ohio State University. “But in this case, we’re talking about mapping functionality at the scale of femtometers – quadrillionths of a meter – the size of an individual proton.
“Now we can take a picture where we can really distinguish the density of gluons at a given angle and radius,” says Brandenburg. “The images are so sharp that we can even begin to see the difference between where the protons and neutrons are arranged inside these large nuclei.”
One consequence of the interaction between the gluon and the photons is what appears to be the discovery of a whole new type of quantum entanglement.
It seems that the resulting positive and negative pions are entangled. “This is the first-ever experimental observation of entanglement between dissimilar particles,” remarks Brandenburg.
“We measure two outgoing particles and it’s clear that their charges are different – they’re different particles – but we see interference patterns that indicate that these particles are entangled or synchronized with each other, even though they’re different. are separate particles,” adds Brookhaven physicist Zhangbu Xu. .
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The discovery has many potential applications beyond the important task of mapping the ways in which the building blocks of matter fit together to create atomic nuclei and ultimately everything we can see and touch.
Quantum entanglement is being researched to one day create much more powerful communication and computing tools than exist today.
The results of the experiment are published in the journal Scientists progress.