Tuning high-Q superconducting resonators by magnetic field reorientation

TL;DR

This paper demonstrates a superconducting resonator whose frequency can be continuously tuned by magnetic field orientation, maintaining high quality factors under strong magnetic fields, which is useful for quantum memory applications.

Contribution

The authors introduce a method to tune superconducting resonator frequency via magnetic field reorientation, preserving high Q-factors at high magnetic fields.

Findings

Resonator maintains Q > 10^5 up to 2.6 T magnetic field.

Achieves 30 MHz frequency tuning by magnetic field rotation.

Tuning is accomplished with a 5 mT perpendicular magnetic component.

Abstract

Superconducting resonators interfaced with paramagnetic spin ensembles are used to increase the sensitivity of electron spin resonance experiments and are key elements of microwave quantum memories. Certain spin systems that are promising for such quantum memories possess 'sweet spots' at particular combinations of magnetic fields and frequencies, where spin coherence times or linewidths become particularly favorable. In order to be able to couple high-Q superconducting resonators to such specific spin transitions, it is necessary to be able to tune the resonator frequency under a constant magnetic field amplitude. Here, we demonstrate a high quality, magnetic field resilient superconducting resonator, using a 3D vector magnet to continuously tune its resonance frequency by adjusting the orientation of the magnetic field. The resonator maintains a quality factor of $> 10^5$ up to magnetic fields of 2.6 T, applied predominantly in the plane of the superconductor. We achieve a continuous tuning of up to 30 MHz by rotating the magnetic field vector, introducing a component of 5 mT perpendicular to the superconductor.