The Standard Model of particle physics is the most comprehensive framework we have for understanding the fundamental particles and forces that shape our universe. It describes the behavior of elementary particles like electrons, quarks, and neutrinos, as well as the fundamental forces that govern their interactions. These forces—electromagnetic, weak, and strong nuclear interactions—are mediated by force-carrying particles like photons, W and Z bosons, and gluons.
One of the most intriguing aspects of the Standard Model is that it represents particles and their antiparticles (such as electrons and positrons) as quantum fields—continuous entities that extend through space and time. Understanding these quantum fields is critical for deciphering the behavior of matter at its most fundamental level. However, simulating the behavior of these fields is an incredibly challenging task, even for the most advanced supercomputers.
The Challenge of Simulating Quantum Fields
Traditional computers, including the most powerful supercomputers, struggle to handle the sheer complexity of quantum field theories (QFTs)—the mathematical frameworks that describe how quantum fields interact. Even quantum computers, which harness the principles of quantum mechanics to perform calculations, face significant hurdles in accurately simulating QFTs.
The main difficulty arises from the nature of force fields, such as the electromagnetic field, which mediates the interactions between charged particles. These fields can vary in direction and strength, making them difficult to encode into the binary logic (0s and 1s) that traditional and quantum computers typically rely on.
In an effort to overcome these limitations, a groundbreaking experiment has demonstrated a new approach using an advanced quantum computing architecture. Researchers at the University of Innsbruck (Austria) and the University of Waterloo (Canada) have successfully simulated quantum electrodynamics (QED), the theory of how charged particles interact via the electromagnetic force, in two spatial dimensions. Their findings, published in Nature Physics, mark a major step toward solving some of the deepest mysteries of particle physics.
A Breakthrough: Quantum Computing with Qudits
Most existing quantum computers operate using qubits—quantum bits that can exist in a superposition of two states (0 and 1). However, this binary approach makes it difficult to accurately represent the continuous nature of quantum fields. The new study takes a radically different approach by using qudits instead of qubits.
What Are Qudits?
Qudits (short for quantum digits) are quantum information units that can encode more than just two states. Unlike qubits, which are limited to 0 and 1, qudits can exist in multiple states simultaneously—such as 0, 1, 2, 3, and 4. This higher-dimensional encoding makes them far better suited for modeling the complex variations in quantum fields.
The research team in Innsbruck developed a qudit-based quantum computer, while their collaborators in Waterloo designed a qudit algorithm tailored for simulating quantum fields. By combining these two innovations, they were able to efficiently store and process quantum information in a way that was previously impossible.
“Our approach enables a natural representation of the quantum fields, which makes the computations much more efficient,” explains Michael Meth, the study’s lead author.
This efficiency allowed the researchers to observe fundamental aspects of QED in two spatial dimensions for the first time—a crucial milestone in the quest to simulate real-world physics on quantum computers.
Why This Matters: Implications for Particle Physics
This breakthrough builds on earlier experiments in 2016, when researchers in Innsbruck successfully simulated the creation of particle-antiparticle pairs. However, that study was limited to a one-dimensional model, meaning that the particles could only move along a straight line.
By extending the simulation to two spatial dimensions, the new research captures a much richer and more realistic picture of quantum electrodynamics.
Key Achievements of the Study
- Beyond One-Dimensional Models – Unlike previous studies where particles were constrained to move along a line, this experiment allows them to move freely in a two-dimensional space, closer to real-world physics.
- Visualization of Magnetic Fields – The researchers were able to observe magnetic fields forming between charged particles, a phenomenon that can only occur in higher-dimensional simulations.
- A New Path Toward Three-Dimensional Simulations – With just a few more qudits, future quantum computers could extend these results into three-dimensional models, unlocking new insights into fundamental physics.
Toward Understanding the Strong Nuclear Force
One of the most exciting possibilities opened up by this research is the ability to simulate the strong nuclear force—the fundamental interaction that holds protons and neutrons together within atomic nuclei. Unlike the electromagnetic force, which is relatively well understood, the strong force remains one of the biggest unsolved puzzles in physics.
Simulating quantum chromodynamics (QCD), the theory that describes the strong force, is notoriously difficult because it involves incredibly strong interactions between quarks and gluons. Traditional methods—such as lattice QCD, which approximates space as a grid—require immense computational power and still struggle with certain calculations.
By leveraging qudit-based quantum computing, researchers hope to finally unravel the mysteries of QCD, leading to potential breakthroughs in fields ranging from nuclear physics to cosmology.
The Future: Quantum Computers as Tools for Fundamental Physics
While the current study is an important step forward, we are still in the early stages of using quantum computers to study fundamental physics. The Innsbruck-Waterloo team’s work demonstrates proof of principle, but scaling up these simulations will require significant technological advancements.
However, the potential rewards are immense:
- More accurate models of fundamental interactions
- Insights into early-universe physics
- Breakthroughs in materials science and quantum chemistry
Physicists believe that as quantum hardware continues to improve, simulations of quantum field theories will become one of the most important applications of quantum computing.
“We are excited about the potential of quantum computers to contribute to the study of these fascinating questions,” says Martin Ringbauer, one of the lead researchers.
As we move forward, quantum computers may soon allow us to explore phenomena that were once beyond our computational reach, bringing us closer to answering some of the deepest questions about the nature of the universe.
Conclusion: A New Era for Theoretical Physics
The simulation of quantum electrodynamics in two dimensions using a qudit-based quantum computer marks an exciting new chapter in physics. By breaking free from the limitations of traditional binary computing, researchers have demonstrated a powerful new approach to studying the universe at its most fundamental level.
From the electromagnetic force to the strong nuclear force, the future of quantum simulations holds extraordinary promise. As quantum computing technology advances, it may soon enable us to unlock the secrets of the cosmos, leading to discoveries that could reshape our understanding of reality itself.
The journey has just begun, but the possibilities are limitless.
Reference: Simulating two-dimensional lattice gauge theories on a qudit quantum computer, Nature Physics (2025). DOI: 10.1038/s41567-025-02797-w