Master thesis defense by Josu Gomez Beldarrain

Characterization of superconducting 5-qubit chips - Towards weight-4 quantum processors

This project focuses on the microwave characterization of five-transmon devices and their readout resonators. Data extraction models for resonators and measurement protocols for qubit chips have been developed. The core of this work is the characterization of four different five-qubit chips and the correlation analysis between the measured parameters and their design specifications. The chip designs range from simple fixed-frequency qubit architectures to more complex configurations incorporating flux lines and couplers.

Energy relaxation times up to 80 µs have been achieved, and conclusions drawn from the results have informed improvements in subsequent device iterations. Additionally, DC crosstalk between qubits has been analysed. Conducted in the context of a newly established and evolving laboratory, some measurements were constrained by hardware limitations. This thesis paves the way for implementing two-qubit iSWAP gates, marking the next step in the group’s progress toward weight-4 quantum processors.