Fabrication and Measurement of Novel Millimeter-wave Superconducting Circuits

While superconducting circuits have revolutionized quantum information processing, the vast majority of these systems are based on microwave-frequency circuits made from aluminum, restricting their quantum operation to mK temperatures. There is a current push to extend the frequencies of these systems to the mm-wave regime, where higher temperature operation would be achievable. However, this presents new challenges as there is very little research into how superconducting circuits behave at mm-wave frequencies. My work focuses on fabricating such high-frequency circuits for low-temperature operation based on superconducting materials such as tantalum and niobium. Using various planar resonator geometries, I will study the behaviour of these circuits at previously unexplored frequencies ranging from 1-40 GHz. I will present details surrounding the design, fabrication, and measurement of these circuits that are optimized for dilution refrigeration measurements. This information will help inform future mm-wave superconducting circuits we plan to make in our group, including planarized optomechanical vacuum gap capacitors and kinetic-inductance-based parametric amplifiers. Such devices will pave the way for quantum-coherent control at higher frequencies, supporting applications in future directions of mm-wave quantum communication, quantum information processing, and fundamental tests of quantum mechanics.