Dual feedback squid magnetometry for sensitive spin detection*

Sensitive detection of spin resonance is essential for achieving coherent spin qubit control¹. Recent experiments have involved bifurcation resonators², and artificial atoms³, which provide sensitivity over a wide frequency range; however, a broadband device is needed for complex materials². A novel differential squid detection method for spin systems on a microwave waveguide is being developed at NHMFL. This method utilizes a superconducting niobium coplanar strip line broadband microwave device coupled with niobium nano-squid devices. A nano-fabricated planar Dayem bridge squid is placed inside an omega loop for sensitive spin detection while a secondary squid is placed far away from the omega loop in order to measure background fields. The differential measurement of the fields measured by the two squids will result in a cancellation of background fields with the goal of having a more sensitive spin detection.

1 G. Yue et al., APL 202601 (2017).
2 Budoyo et al., PRM 2.1, 011403 (2018).
3 Toida et al., Comm. Phys. 2.1, 33 (2019).