Effective method of forming and detecting a fractional magnetic flux quantum

Abstract We developed a minimal method of forming and detecting a fractional magnetic flux quantum in a two-component superconductor fabricated using an ultra-thin niobium bilayer that sandwiches a Josephson barrier. The fractional quantum created by cooling a bilayer disk in the magnetic field survived after turning off the magnetic field. The survived quantum was confirmed by the change in the critical current of a superconducting quantum interference device (SQUID) placed on the bilayer disk. By replacing a flux qubit with the SQUID, we can use the fractional flux quantum as the flux bias for the flux qubit. This method enables the investigation of fractional quantization and the related topology.