Exploring the Proton’s Hidden Depths

The proton’s interior is one of the most dynamic and elusive frontiers in physics. Inside this minuscule particle, quarks and gluons engage in an ever-changing dance within a sea of virtual particles. Now, leveraging quantum information theory and the principles of quantum entanglement, scientists have crafted a groundbreaking framework to describe these interactions with remarkable clarity.

Figure 1. Unveiling a Hidden Quantum World Inside the Proton – Stranger Than We Ever Thought.

For the first time, this innovative approach accurately explains data from all known experiments involving the scattering of secondary particles during deep inelastic collisions between electrons and protons. This milestone achievement comes from an international collaboration of theorists from Brookhaven National Laboratory (BNL) and Stony Brook University (SBU) in New York, Universidad de las Américas Puebla (UDLAP) in Mexico, and the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow. Figure 1 shows Unveiling a Hidden Quantum World Inside the Proton – Stranger Than We Ever Thought.

Probing the Proton’s Interior

To uncover the mysteries within a proton, scientists rely on high-energy collisions between protons and electrons. “If we want to learn about the phenomena taking place inside a proton, we first have to get there somehow,” explains Prof. Krzysztof Kutak from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN). Electrons are ideal for this task because they are much smaller than protons and, as elementary particles, they do not break down into smaller components, ensuring the purity of the interaction.

A Turbulent Sea of Quarks and Gluons

Unlike electrons, protons are not elementary particles. They are composed of three valence quarks—two up quarks and one down quark—held together by gluons, the carriers of the strong nuclear force. However, the interior of a proton is far from simple. The intense interactions within create a dynamic environment where virtual quark-antiquark pairs, including heavy quarks like charm, and virtual gluon pairs constantly emerge and vanish. This ever-shifting sea of particles reflects the complex nature of the strong force at work inside the proton.

Quantum Entanglement Within the Proton

In this groundbreaking research, scientists propose that despite the proton’s minuscule size, its internal components—quarks and gluons, collectively known as partons—are quantum entangled. Quantum entanglement occurs when the properties of one particle instantly influence another, regardless of the distance separating them, without the need for information to physically travel between them.

“In the case of the interior of the proton, entanglement occurs at unimaginably small distances—less than a quadrillionth of a meter—and it’s a collective property,” explains Prof. Martin Hentschinski from Universidad de las Américas Puebla (UDLAP). “Our earlier studies have shown that this phenomenon doesn’t affect just a few partons but all of them within the proton.”

Unveiling Entanglement Through High-Energy Collisions

To explore this entangled state, researchers rely on high-energy collisions where an electron strikes a proton, triggering an electromagnetic interaction mediated by a photon. In deep inelastic collisions, the photon’s energy is so intense that its electromagnetic wave can penetrate the proton, revealing intricate details of its inner structure.

This interaction causes the proton to break apart, producing a cascade of secondary particles. Interestingly, quantum entanglement reveals itself in the correlation between the number of particles produced from the region of the proton impacted by the photon and the overall number of observable hadrons formed after the collision.

Quantifying Entanglement with Entropy

To measure this entanglement, scientists turn to the concept of entropy, a key metric in both complex systems and quantum information. “If we could access every detail of the proton’s entanglement through deep inelastic collisions, the entanglement entropy would be zero,” notes Prof. Dmitri Kharzeev from Stony Brook University (SBU) and Brookhaven National Laboratory (BNL).

However, because the photon only interacts with part of the proton, leaving the rest hidden, the entanglement entropy is greater than zero. This provides a valuable measure of the extent of quantum entanglement within the proton.

Experimental Validation and Data Insights

The international team demonstrated that entanglement entropy could predict the distribution of hadrons produced during electron-proton collisions. This maximal entanglement means it’s fundamentally impossible to determine precisely how many particles will emerge from any given collision—a hallmark of quantum uncertainty.

These theoretical predictions were confirmed using data from the H1 experiment at the HERA particle accelerator in Hamburg, conducted between 2006 and 2007. In these experiments, single protons collided with positrons (the antimatter counterparts of electrons), providing critical validation for the new framework.

“We’ve been studying proton entanglement for years,” says Dr. Zhoudunming Tu of BNL. “While previous work focused on specific datasets, we’ve now unified all deep inelastic scattering data under a single, universal formalism.”

Looking Ahead: Future Colliders and New Discoveries

The team anticipates that this generalized theoretical framework will be instrumental in analyzing data from next-generation particle colliders, such as the Electron-Ion Collider (EIC) set to launch at Brookhaven Laboratory in the coming decade. Unlike previous experiments, the EIC will facilitate collisions between electrons and not just protons, but also heavier ions, offering new opportunities to probe nuclear matter.

Combined with fresh experimental data, this approach could unlock answers to some of the most profound questions in nuclear physics.

Redefining Our Understanding of Nuclear Matter

“We now have strong evidence that our formalism, which incorporates entanglement entropy, is not just coincidentally aligned with experimental observations,” concludes Prof. Kutak. “It genuinely explains the nature of the phenomena we observe. By delving deeper into entanglement entropy, we hope to gain a better understanding of how strong forces bind quarks and gluons within protons—and how a proton’s behavior changes when it’s part of a larger atomic nucleus.”

Source: SciTECHDaily

Cite this article:

Priyadharshini S (2025),Physicists Discover a Hidden Quantum Realm Within the Proton – And It’s Stranger Than We Imagined, AnaTechmaz, pp. 197