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.