Scientists at the University of Oxford have used a hybrid quantum computer to reproduce a phenomenon in which a particle can experience the influence of a magnetic field without passing through the field itself. During the experiment, they managed to completely stop the motion of a simulated particle, demonstrating how quantum phenomena can alter the behavior of matter.
The experiment reproduced the Aharonov–Bohm effect, predicted by physicists Yakir Aharonov and David Bohm in 1959. According to this effect, the quantum state of a charged particle can change under the influence of magnetic flux, even if the particle travels outside the region where the magnetic field is present. The effect was later confirmed in experiments involving real electrons.
For their experiment, the scientists combined two quantum components: qubits and quantum oscillators. The qubits represented the fields, while the oscillators represented matter. Using these components, the researchers built a simple ring-shaped system in which two oscillators represented a particle of matter at two different positions, while two qubits represented the fields connecting those positions.
The researchers placed the qubits in an entangled quantum state, which represented the magnetic flux passing through the center of the ring in the model. Initially, the particle was able to move around the ring through quantum tunneling. However, as the magnetic flux increased, the quantum phases of the two possible paths changed, causing their effects to cancel each other out. As a result, tunneling stopped completely, and the simulated particle remained in its initial state.
The study showed that the Aharonov–Bohm effect can also be investigated in a system where the field itself participates in quantum changes. The findings were published in the scientific journal Nature Physics.
Such systems could help researchers study interactions between matter and fields associated with fundamental forces, calculations of which are too complex for conventional computers. Alongside the Oxford research, a team at the University of Maryland led by Professor Norbert Linke used a hybrid quantum system to simulate the Yukawa potential, a mathematical description of an interaction used in nuclear and particle physics. Both teams' studies were also published in Nature Physics.
The significance of this experiment lies not only in the scientists' reproduction of a quantum phenomenon predicted more than six decades ago. They also demonstrated that it is possible to study the phenomenon in a system where the field is not merely an external condition but actively participates in the changes. This gives researchers an opportunity to move closer to investigating physical models that become increasingly difficult to calculate with classical computers as the systems grow more complex.
However, the experiment is currently limited to a small, specially designed quantum system; it does not demonstrate that the motion of real particles can be stopped under any conditions. The next challenge is to test this approach on more complex systems. The parallel work at the University of Maryland also shows that hybrid quantum systems can be used to investigate different fundamental interactions, although further research is still needed to assess their practical capabilities.
