Modelled Spin Sensitivity of nanoSQUIDs in Different Configurations

Micro- and nano-sized superconducting quantum interference devices (SQUIDs) allow the measurements of extremely low magnetic moment. In the last decade, many efforts have been devoted to the study and the development of these quantum sensors at a nanometric scale (nanoSQUIDs). In this paper, a study of performance of these nanosensors in different configurations is presented. In particular, the magnetic flux coupling and the spin sensitivity have been computed for planar nanoSQUIDs in square and rectangular shapes in the presence of an elementary magnetic moment (Bohr magneton). The computation has been carried out as a function of the position of the Bohr magneton within the sensitive SQUID loop and for different distances from the loop plane. The same characteristics have also been computed for a square nanoSQUID as a function of side length taking into account the increase of the magnetic flux noise as a function of the loop inductance. In addition, a configuration including a nonflat geometry has been analyzed.