Solid-state spin ensembles addressed via superconducting circuits are promising candidates for quantum memory applications, offering multimodal storage capability and second-long coherence times at their clock transition. Implementing practical memory schemes requires dynamic control over both the resonator frequency and bandwidth. In this letter, we report measurements of a superconducting resonator whose frequency can be tuned by passing a DC current through the high-kinetic-inductance thin film, and whose bandwidth can be tuned by parametric coupling to a low-Q buffer resonator. Using this resonator, we address an ensemble of bismuth donors at their clock transition, measuring a Hahn-echo coherence time of 450 ms. We demonstrate RF driving of the bismuth donor hyperfine transitions, as well as dynamic bandwidth control of the resonator.
@article{arxiv.2510.19684,
title = {Addressing spins at the clock transitions with a frequency- and bandwidth-tunable superconducting resonator},
author = {Yutian Wen and V. Ranjan and T. Lorriaux and D. Vion and B. Huard and A. Bienfait and E. Flurin and P. Bertet},
journal= {arXiv preprint arXiv:2510.19684},
year = {2025}
}