Deep inside the heart of every atom lies a story that physicists are only beginning to understand—a quantum drama playing out between the smallest constituents of matter: quarks and gluons. These tiny particles, trapped inside protons and neutrons, are now revealing behavior so bizarre it defies classical logic. In a groundbreaking study, researchers at Stony Brook University and Brookhaven National Laboratory have uncovered compelling evidence that quarks and gluons exhibit maximal quantum entanglement at high energies—a finding that could rewrite our understanding of how matter forms and behaves at the subatomic scale.
At first glance, a proton may seem like a simple thing—a positively charged particle found in the nucleus of every atom. But peek beneath the surface, and you’ll find a churning sea of quarks, gluons, and a flurry of fleeting quantum fluctuations. These particles are bound together by the strongest force in nature: the strong nuclear force, governed by the rules of quantum chromodynamics (QCD). Yet, despite decades of study, one of QCD’s greatest mysteries has remained elusive: how do free-floating quarks and gluons “hadronize”—that is, how do they bind together to form protons, neutrons, and other detectable particles?
The answer, it seems, might lie in the spooky realm of quantum entanglement.
Quantum Entanglement Inside Protons?
Entanglement is one of the most counterintuitive concepts in quantum mechanics. When two particles are entangled, their states are so deeply linked that measuring one instantly affects the other—even if they’re separated by vast distances. Einstein famously called this “spooky action at a distance,” and for decades, it remained a curiosity in the lab. But the new study suggests it may be happening naturally inside every proton, all the time.
Charles Joseph Naim, a physicist and the corresponding author of the study published in Physical Review Letters, explains:
“Our study originated from the intriguing observation that the internal structure of protons at high energies exhibits maximal quantum entanglement. This concept suggests that the quarks and gluons inside a proton are interconnected in such a way that the state of one instantly influences the state of another, regardless of distance.”
This goes far beyond what scientists previously imagined. It suggests that protons aren’t just bags of particles bumping into each other—they’re highly correlated quantum systems where changes in one part of the proton affect the whole.
From Jets to Hadrons: Probing Entanglement Through Particle Collisions
To explore this phenomenon, Naim and his team turned their attention to the data coming from the Large Hadron Collider (LHC), the world’s most powerful particle accelerator located at CERN. In high-energy proton-proton collisions, the quarks and gluons inside each proton smash into each other, creating jets—sprays of particles that shoot out like fireworks from the collision site.
But these jets don’t just form randomly. They follow patterns, shaped by the underlying physics of how particles like quarks and gluons transform into hadrons—a process known as hadronization. By analyzing how particles are distributed within these jets, the researchers aimed to test whether quantum entanglement had any predictive power in this chaotic subatomic landscape.
Using data from the ATLAS Collaboration, the team compared fragmentation functions—mathematical descriptions of how quarks and gluons evolve into jets of hadrons—with predictions derived from their entanglement framework. What they found was striking.
“By applying the framework of maximal entanglement,” said Naim, “we established a relationship between the fragmentation function and the entropy—a measure of disorder or complexity—of the produced hadrons.”
In other words, the patterns in jet formation weren’t random after all. They matched the patterns you’d expect if the initial quarks and gluons were maximally entangled—a deeply connected state that persisted even as the particles separated and transformed.
Quantum Chromodynamics, Entropy, and a New Frontier
This research bridges two very different regimes of physics: the perturbative (where calculations based on QCD work well) and the non-perturbative (where things get too messy for traditional methods). Hadronization falls squarely in the latter category—it’s a black box that physicists have long struggled to open.
But by viewing hadronization through the lens of quantum information theory, Naim and his colleagues have found a new way to peek inside. Their model connects the entropy of produced particles—essentially a measure of how complex or chaotic the system is—to the entanglement of the quarks and gluons that gave rise to them.
It’s a radical idea: information theory—originally developed for computer science and telecommunications—could help solve one of the deepest mysteries in high-energy physics.
“This approach offers a novel perspective on the transition from perturbative to non-perturbative quantum chromodynamics,” said Naim. “It provides a theoretical bridge where previously there was only a gap.”
Color Confinement and the Entanglement Puzzle
One of the most enduring puzzles in QCD is the phenomenon known as color confinement. Despite being responsible for the strong force, individual quarks and gluons have never been observed in isolation. They’re always confined within hadrons—a quirk of nature that no current theory fully explains.
Could quantum entanglement hold the key?
Naim and his team believe that their findings might one day help solve this riddle. If quarks and gluons are indeed maximally entangled, then their fates are inherently linked—making it impossible to isolate one without affecting the others. This deeply woven fabric of quantum connectivity could be nature’s way of enforcing confinement.
It’s still early days, but the implications are profound. If entanglement plays a foundational role in how matter binds together, it could lead to a unified theory that connects quantum mechanics, information theory, and the strong nuclear force in a way that’s never been done before.
The Road Ahead: From Protons to Nuclei
So where does this research go next? According to Naim, the journey has just begun.
“Building on our current work, we plan to further investigate the role of quantum entanglement in various hadronization processes and possibly in nuclei,” he said. “Future research will involve analyzing data from upcoming experiments at facilities like the Electron-Ion Collider (EIC).”
The EIC, currently under construction in the United States, is poised to be the next great tool for probing the quantum structure of matter. It will allow scientists to smash electrons into protons and nuclei with unprecedented precision, opening a new window into the entangled world of subatomic particles.
Moreover, the team hopes to develop more sophisticated models that incorporate principles from quantum information science. These models could one day make it possible to simulate hadronization with far greater accuracy, transforming the way we interpret results from high-energy physics experiments.
Conclusion: A New Quantum View of the Proton
The discovery that quarks and gluons inside protons might be maximally entangled is more than just a scientific curiosity—it’s a potential game-changer. It suggests that the very building blocks of matter are not just connected by forces, but by information itself. And in doing so, it pushes the boundaries of what we thought was possible in quantum physics.
By blending insights from QCD, quantum mechanics, and information theory, researchers like Naim are charting a bold new path—one that could finally crack open the mysteries of hadronization, color confinement, and perhaps even the origins of mass itself.
In the ever-evolving quest to understand the universe at its most fundamental level, this work reminds us of one profound truth: even inside something as seemingly simple as a proton, the universe hides layers of complexity we are only beginning to unravel.
Reference: Jaydeep Datta et al, Entanglement as a Probe of Hadronization, Physical Review Letters (2025). DOI: 10.1103/PhysRevLett.134.111902