Researchers at the University of Oxford demonstrated the Aharonov-Bohm effect using trapped ions to simulate a Z₂ lattice gauge theory in a quasi-two-dimensional loop, according to a study published in Nature Physics.
The team used two strontium ions in a hybrid trapped-ion quantum computer. Electronic states of the ions encoded gauge fields, while vibrations encoded matter. By coupling the ions' qubits and vibrational modes in specific ways, the researchers created synthetic dimensions that formed a loop with two paths between two matter sites.
The researchers entangled the two qubits to encode magnetic flux through the loop. One entangled state represented zero flux, the other represented nonzero flux. They used lasers to make a single phonon (representing a matter particle) hop between sites. Each hop switched whether a field line was present or absent on the link.
When both qubits were entangled in the zero-flux state, both paths gave the particle the same phase, so they added up. The particle tunneled between sites twice as fast as on a single link. When entangled in the state representing a vison, the two paths gave opposite phases that canceled out. The particle stayed in place.
Sebastian Saner, the study's first author, noted that the most difficult part was combining the different experimental ingredients. Earlier simulations of Z₂ lattice gauge theories using cold atoms or superconducting qubits occurred mostly in one dimension, where magnetic flux effects cannot appear. Most two-dimensional setups removed matter fields to simplify the model, preventing study of how moving charges and flux influence each other.