Polymer-loaded three dimensional microwave cavities for hybrid quantum systems

Abstract

Microwave cavity resonators are crucial components of many quantum technologies and are a promising platform for hybrid quantum systems, as their open architecture enables the integration of multiple subsystems inside the cavity volume. To suspend these subsystems within the centre of a cavity where field strengths are strong and uniform, auxiliary support structures are often required, but the effects of these structures on the microwave cavity mode are difficult to predict due to a lack of a priori knowledge of the materials’ response in the microwave regime. Understanding these effects becomes even more important when frequency matching is critical and tuning is limited, for example, when matching microwave modes to atomic resonances for atomic vapour cells inside enclosed microwave cavities. Here, we study the microwave cavity mode in the presence of three commonly-used machinable polymers, paying particular attention to the change in resonance and the dissipation of energy. We demonstrate how to use the derived dielectric coefficient for cavity design in a test case, wherein we match a polymer-filled 3D microwave cavity to a hyperfine transition in rubidium.