  We have designed and investigated a contactless magnetic phase shifter for
flux-based superconducting qubits. The phase shifter is realized by placing a
perpendicularly magnetized dot at the centre of a superconducting loop. The
flux generated by this magnetic dot gives rise to an additional shielding
current in the loop, which, in turn, induces a phase shift. By modifying the
parameters of the dot an arbitrary phase shift can be generated in the loop.
This magnetic phase shifter can, therefore, be used as an external current
source in superconducting circuits, as well as a suitable tool to study
fractional Josephson vortices.
