Tuning a 3D Microwave Cavity via Superfluid Helium at MilliKelvin Temperatures

TL;DR

This paper demonstrates a method to tune a superconducting 3D microwave cavity at cryogenic temperatures using superfluid helium, enabling precise frequency adjustments without mechanical parts and maintaining high quality factors.

Contribution

The study introduces a novel dielectric tuning technique for 3D microwave cavities using superfluid helium at milliKelvin temperatures, avoiding mechanical actuation.

Findings

Achieved percent-level frequency tuning of the cavity

Maintained high quality factor of 3×10^5 during tuning

Demonstrated dielectric property-based tuning at cryogenic temperatures

Abstract

Frequency tunability of 3D microwave cavities opens up numerous possibilities for their use in hybrid quantum systems and related technologies. For many applications it is desirable to tune the resonance at cryogenic temperatures without mechanical actuation. We show that a superconducting 3D microwave cavity can be tuned at the percent level by taking advantage of the dielectric properties of superfluid $^4$He at milliKelvin temperatures, without affecting its intrinsic quality factor -- reaching $3\times10^5$ in the present experiment.