Quantum supercurrent in a quantum dot Aharonov-Bohm interferometer

The quantum supercurrent through an Aharonov-Bohm interferometer containing four quantum dots is investigated theoretically. The dependence of the supercurrent on the arrangement of the four quantum dot energy levels is obtained. For various quantum dot energy levels, the supercurrent shows different numbers of resonant peaks. By tuning the magnetic flux, the sign of the supercurrent can be changed, which results in the π-junction transition. Whether the magnetic flux can reverse the supercurrent depends distinctly on the four quantum dot energy levels. This opens the possibility to manipulate the quantum supercurrent by varying the magnetic field and the gate voltage.