Dynamical Sweet Spot Manifolds of Bichromatically Driven Floquet Qubits

Flux-tunable superconducting circuits are vulnerable to noise induced dephasing except at sparse flux bias sweet-spots, limiting the utility of the flux control. Replacing the DC flux bias with an AC signal reveals continuous manifolds of noise protected dynamical sweet spots, allowing for flux modulation while limiting dephasing. Here, we utilize Floquet theory to analyze the dynamical sweet spots induced by weak and strong bichromatic flux drives. Specifically, we characterize the Floquet quasienergy spectrum, multiphoton resonance (AC stark shift and power broadening), and dephasing lifetime for a two level system as functions of the driving frequencies and AC amplitudes. We obtain a maximal dephasing lifetime when both driving strengths are non-negligible, suggesting a better lifetime with bichromatic driving compared to the monochromatic case.