A new type of quantum entanglement observed in gold ions

A new type of quantum entanglement observed in gold ions

A new type of quantum entanglement observed in gold ions

Nuclear physicists have used a never-before-seen type of quantum entanglement to help them gain information about the interior of the atomic nucleus.

At the Relativistic Heavy Ion Collider (RHIC), a particle collider at the US Department of Energy’s Brookhaven Laboratory in the US, physicists were able to use photons (particles of light) surrounding gold ions passing through the collider to observe the atomic structure of the nucleus and entangled pairs of particles.

Called “spooky acting at a distance” by Einstein, quantum entanglement connects the physical states of particles, no matter how far apart they are. So far, quantum entanglement has only been observed between particles of the same type, such as entangled pairs of electrons or photons.

In their experiment, nuclear physicists watched photons interact through a series of quantum fluctuations with gluons in gold ions, jumping through RHIC. The cleverly named gluons are – wait for it – the glue-like particles responsible for the strong force that holds the quarks – which in turn form the protons and neutrons in atomic nuclei – together.


Read more: Quantum entanglement of many atoms observed for the first time


A new intermediate particle is formed by the interaction between photons and gluons. This particle quickly decays into oppositely charged particles called ” pions ” (denoted by the Greek letter π). Speed ​​and trajectory π+ and π can be used to obtain key information about the photon and to determine the distribution of gluons in the nucleus more precisely than ever before.

Schematic-showing-tangled-verts
Left: Scientists use the STAR detector to study gluon distribution by tracking pairs of positive (blue) and negative (magenta) pions (π). These π pairs come from the decay of the rho particle (purple, ρ0) – generated by interactions between photons surrounding one rushing gold ion and gluons in another passing very close without colliding. The closer the angle (Φ) between π and the rho trajectory is to 90 degrees, the clearer the scientists’ view on the distribution of gluons. Right/inset: Measured π+ and π- particles experience a new type of quantum entanglement. Here’s the proof: when nuclei pass by each other, it’s as if two rho particles (purple) are generated, one in each nucleus (gold) at a distance of 20 femtometers. As each rho decays, the wavefunctions of the negative pions from each decay of rho interfere and amplify each other, while the wavefunctions of the positive pions from each decay do the same, resulting in one π+ and one π- wavefunction (aka particle) striking detector. These reinforcement patterns would not be possible if π+ and π- were not entangled. Source: Brookhaven National Laboratory.

“This technique is similar to the way doctors use positron emission tomography (PET scanning) to see what’s going on in the brain and other parts of the body,” says former Brookhaven Lab physicist James Daniel Brandenburg, now an assistant professor at Ohio State university. “However, in this case we are talking about mapping objects to scale femtometers – quadrillionths of a meter – the size of a single proton.”

“Now we can take a picture where we can really distinguish the density of gluons at a given angle and radius,” explains Brandenburg. “The images are so precise that we can even begin to see the difference between the distribution of protons and neutrons inside these large nuclei.”

The consequence of the interaction between gluon and photons is what appears to be the discovery of a whole new kind of quantum entanglement.

The resulting positive and negative pions appear to be entangled. “This is the first-ever experimental observation of the entanglement of different particles,” notes Brandenburg.

Physicists-at-the-wire-collision-detector
Daniel Brandenburg and Zhangbu Xu at the Relativistic Heavy Ion Collider (RHIC) STAR detector. Source: Brookhaven National Laboratory.

“We measure two outgoing particles and clearly their charges are different – they are different particles – but we see interference patterns that indicate that these particles are entangled or synchronized with each other, even though they are distinguishable particles,” adds Brookhaven physicist Zhangbu Xu .


Read more: Quantum entanglement can be used to encrypt messages – increasing data security


The discovery has many potential applications beyond the important task of mapping the ways the building blocks of matter come together to form atomic nuclei, and ultimately everything we can see and touch.

Quantum entanglement is being studied to one day create much more powerful communication and computing tools than those that exist today.

The results of the experiment are published in a journal Science progress.


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