Method and apparatus for nano-scale SQUID

A nano-SQUID (superconducting quantum interference device) method and system for detecting a magnetic field associated with a nano-sample. A magnetic field of a nano-sample (1130) is coupled through the nano-SQUID hole/loop (720), by placing the sample within the SQUID loop. A static field (Bp) is applied across the nano-SQUID, substantially perpendicular to a sensitivity axis of the nano-SQUID. A perturbation field (Bm) is applied across the nano-SQUID, substantially perpendicular to the sensitivity axis of the nano-SQUID and substantially perpendicular to the static field. A behaviour of the magnetic field of the nano-sample caused by the static field and perturbation field is monitored by monitoring an output of the nano-SQUID. The nano-SQUID can be operated in open loop mode without flux locked loop.