Collective excitations of microchannel-confined electrons on helium

Electrons floating above the surface of superfluid helium (eHe) are a unique platform to investigate the high-frequency collective dynamics of ultra-high mobility trapped electron systems. Here we present the results of recent experiments in which the electron system is simultaneously subjected to microchannel confinement and GHz-frequency microwave excitation. The microchannel device provides precision control of the electron density and enables access to both quasi-one-dimensional electron chains as well as two-dimensional electron sheets. In this device, we observe density-dependent resonant-like features in the electron transport data, which originate from collective excitations of the electron system in the microchannel. Additionally, we present progress on developing hybrid devices composed of microchannel eHe systems coupled to superconducting coplanar waveguide resonators, which can aid in the development of future quantum information science technologies based on trapped electrons.