Scientists Recreate Quantum Effect That Prevents Particles From Cooling Down

The experiment reproduced the Aharonov–Bohm effect. In this phenomenon, a charged particle moving around a region containing magnetic flux undergoes a measurable change in its quantum state, even though its path does not pass through the magnetic field itself.

The University of Oxford team used a quantum system that combines a qubit—the fundamental unit of quantum information—with a quantum oscillator representing vibrational motion. Their findings show how this combination can help scientists study fundamental interactions between matter and fields that are increasingly difficult to simulate using traditional computers.

The strange quantum effect predicted in 1959

In everyday physics, charged particles react to the electric and magnetic fields they encounter. Quantum mechanics, however, reveals that particles can behave in ways that have no direct counterpart in ordinary experience.

In 1959, physicists Yakir Aharonov and David Bohm predicted that charged particles could be affected by magnetic flux even if they moved completely outside the region containing the magnetic field. Rather than experiencing a conventional magnetic force along its path, the particle undergoes a change in its quantum phase.

Quantum phase describes an aspect of a particle’s wave behavior that affects how different possible paths interfere with one another. Although phase itself is not directly visible, differences in phase can produce measurable effects.

This prediction became known as the Aharonov–Bohm effect and was eventually verified in experiments using real electrons. It is one of the clearest demonstrations that the quantum world operates according to rules that go beyond the familiar laws of classical physics.

Researchers are now investigating how this phenomenon works in a more complex theoretical system known as lattice gauge theory.

Lattice gauge theories describe how matter interacts with fields associated with fundamental forces. They represent space as a grid, with matter located at individual points and fields associated with the connections between those points. Such models are especially important in particle physics and high-energy physics, where scientists study the fundamental particles and interactions that make up the universe.

The challenge is that, as these systems become more complex, the mathematics becomes much more demanding. Even powerful classical computers can struggle to calculate how all the interacting components evolve.

Quantum computers offer a different approach. Instead of calculating every aspect of a quantum system with classical computing techniques, scientists can build another quantum system that follows the same underlying rules. This approach, known as quantum simulation, allows researchers to observe the system’s behavior directly.

How the Oxford team built the quantum experiment

The Oxford project began in 2022, when lead authors Dr. Sebastian Zahner, Dr. Oana Bazavan, and their colleagues began developing a method for simulating lattice gauge theories with hybrid quantum systems. They collaborated with Dr. Alejandro Bermúdez of the Teorica Institute in Madrid.

The experimental design relied on two different quantum components, each with a separate function.

The first was a qubit encoded in the internal state of a trapped ion—a charged atom held in place by an electromagnetic field. These qubits represented the gauge field in the theoretical model.

The second component was a quantum oscillator created by the vibrations of the same trapped ions. These oscillators represented matter.

By combining the two components, the researchers constructed a simple loop that served as the basic building block of lattice gauge theory. The two oscillators represented matter at different locations, while the two qubits represented the field connecting those locations.

Although the arrangement was small, it was sufficient to reproduce the important interaction between matter and magnetic flux.

Quantum entanglement creates a surprising result

The researchers placed the two qubits into an entangled state. Entanglement is a phenomenon in which quantum systems become linked in ways that cannot be fully explained by classical physics.

In the lattice gauge theory being simulated, this entangled state represented magnetic flux passing through the center of the loop.

Initially, the researchers planned to introduce the magnetic flux as a fixed background condition. However, creating the necessary interactions requires capabilities that the quantum hardware did not have.

Encoding the magnetic flux directly into the qubits provided a practical alternative. More importantly, it allowed the magnetic flux to become part of an evolving quantum system instead of remaining an immutable external influence.

“For us, the exciting step was to encode the magnetic flux into a gauge field that is itself dynamic,” says Dr. Zahner. “Rather than evolving matter in a fixed background, matter and gauge fields become part of the same quantum mechanics.”

What began as a technical workaround ultimately allowed the researchers to explore a more complex version of the phenomenon, in which matter and fields participate together in quantum mechanics.

How magnetic flux stopped simulated particles from moving

The scientists set up simulated loops to study how matter particles move between locations through a process known as quantum tunneling.

Quantum tunneling allows particles to move between states in ways that are not possible under ordinary classical rules.

When the researchers ran the simulation without magnetic flux, the particles were able to tunnel freely through the loop.

The results changed significantly when simulated magnetic flux was introduced.

The particles had two possible paths around the loop, but the magnetic flux changed their relative quantum phases. The two paths then interfered destructively, causing their quantum contributions to cancel one another out.

This interference completely suppressed tunneling, leaving the simulated particles frozen in their original states.

The result demonstrated the Aharonov–Bohm effect within a lattice gauge theory involving a dynamical field. Rather than simply reproducing the familiar behavior of particles moving around a fixed magnetic influence, the experiment showed how the phenomenon appears when both matter and field are represented by interacting quantum components.

New quantum tools for exploring fundamental physics

The University of Oxford study was published alongside related work by researchers at the University of Maryland, led by Professor Norbert Linke.

The Maryland team also used a hybrid quantum system, but its experiments focused on simulating the Yukawa potential, a mathematical description of interactions relevant to nuclear and particle physics.

The two research groups developed their methods independently before coordinating their research submissions.

Together, the experiments demonstrate that hybrid quantum computers can provide valuable tools for investigating fundamental interactions that are difficult to reproduce with classical simulations.

By combining different types of quantum components, researchers can build systems that represent matter and fields in ways that more closely reflect the physics they want to study.

The Oxford experiment shows what this approach can achieve. A phenomenon first predicted in 1959 and later observed in electrons has now been recreated in a quantum simulator in which the fields themselves participate in the dynamics. This gives scientists another way to explore the unusual laws governing the quantum world.