Addressing spins at the clock transitions with a frequency and bandwidth-tunable superconducting resonator*

Among platforms for storing quantum states in the microwave domain, solid state spin ensembles addressed via superconducting circuits stand out for their multimodal storage capability and the second-long coherence time when operated at clock transitions.

Successful implementation of a practical memory scheme requires however several keys features, such as the ability to tune on-demand the frequency and the bandwidth of the resonator. In this talk we will present a superconducting circuit architecture accomplishing both, allowing strong coupling to an ensemble of bismuth dopants in silicon. We devise a parametric process to dynamically control the virtual bandwidth of the superconducting circuit by exploiting its kinetic inductance nonlinearity, demonstrating coupling rate tuning range over a factor of 15 and thus enabling catch-and-release of microwave photons. We also observe a coherence time of T2=450 ms at the clock transition.