21st Patras Workshop on Axions, WIMPs and WISPs

A Novel Qubit Sensor Fabrication Technique Toward High Frequency Direct Excitation Dark Photon Searches

Not scheduled

20m

University of Western Australia

Student/ECR Presentation

Speaker

Koki Aoyanagi (Kyoto University)

Description

Qubit-based readout technologies enable a SQL-free sensitivity in dark matter haloscope experiments, particularly in the high frequency regime (>5GHz). We are developing high frequency superconducting qubit detectors for direct excitation dark-photon searches above 20 GHz, where suitable devices have not yet been established. Toward this goal, we introduced a “double-oblique evaporation” technique for qubit Josephson junction fabrication, enabling a simpler and more reproducible process without electron-beam lithography [1]. Room-temperature resistance measurements of test junctions confirmed successful junction formation with a high fabrication yield, demonstrating the reproducibility of the process. A transmon qubit fabricated with this technique was characterized in a three-dimensional microwave cavity at 20 mK and showed a relaxation time of 9.2 μs. This result provides a basis for extending the device frequency toward the >20 GHz regime required for direct dark photon searches. In this talk, we also report the status of the search experiment incorporating this sensing technique.

[1] K. Aoyanagi et al., arXiv:2605.19590v1