Absolute magnetometry by dc-SQUID arrays

SQUID magnetometers are usually considered sensitive only to changes of the magnetic field, since their response is a periodic function of the linked magnetic flux. However, by using a series array of a few, properly designed dc-SQUIDs, it is possible to realize a device capable of detecting also the absolute value of the flux: the voltage-to-magnetic flux characteristic of this device is not periodic and displays an absolute minimum at the point of zero field. Here we present the working principle of the device, the simulated expected behavior and the preliminary experimental results on a prototype.