Tuning the energy gap of a flux qubit by AC-Zeeman shift

We propose to tune the minimal energy level splitting of a superconducting qubit by a microwave induced ac Zeeman shift. We experimentally investigate the usability of this approach to overcome parameter spread induced by the micro fabrication of superconducting artificial quantum circuits. To do so, we dress the qubit by a strong tone, effectively shifting its energy levels. By a two-tone spectroscopy of this dressed system the shift of the qubit’s energy levels can be probed. A theoretical treatment allowed us to completely explain the observed experimental dependencies and reconstruct the influence of the strong driving to the dissipative dynamics of the qubit.