STSM of Simon Collienne at Center for Quantum Science and LISA+ (Germany): Noise measurements in electroannealed Nb-based nanoscale SQUIDs

During the last years, the interest for the magnetic response of nanoscale systems has launched a number of initiatives to miniaturize dc SQUID devices. In this endeavor, conventional tunnel Josephson junction are less attractive, since their low critical current density prevents them to achieve optimum performance. With the goal to mitigate this drawback, a growing attention has been devoted to Dayem bridge junctions made of a high critical current density material such as Nb. The main scientific objective of the mission, was to complete the ongoing investigation of Nb μSQUIDs with weak links tuned by electroannealing with measurements of the flux noise spectrum at different stages of the EA process. The funding provided by COST allowed us to achieve the goals of this project and publish the scientific results on the optimization of the performance of a SQUID sensor in the journal Phys. Rev. Appl., 15, 034016 (2020).