Tunable on-chip readout resonator in the W-band

Readout resonators are an integral part of all circuit QED (cQED) setups as it enables QND measurement on the qubit state. In this work, we demonstrate superconducting “Ouroboros” resonators in the W-band (75-110 GHz). Previously we were able to design and tune quarter-wavelength NbTiN resonators with DC bias lines and radial stub filters to optimize the RF response [1]. But rescaling devices with different sheet inductances require complete redesigning of all circuit components which is labor intensive. Hence, the goal of this work is to demonstrate easy tunability of the resonator using the Meissner effect. We will present finite element electromagnetic simulations alongside measurement results on fabricated devices. Achieving this takes us one-step closer to implementing a cQED system at the millimeter-wave frequencies.

[1] D. Das, et al., "Superconducting on-chip tunable mm-wave resonator" , doi: 10.1109/IRMMW-THz50927.2022.9895550.