A magnetometer for measuring a magnetic flux and also the absolute magnetic flux, the magnetometer comprising a plurality of superconducting quantum devices (SQUIDs) connected in series, each SQUID including: a superconducting loop containing two Josephson junctions connected to each other in parallel; and a flux-focussing region, the flux-focussing region configured to generate a screening current in response to the magnetic flux, the screening current modulating the corresponding voltage response for each SQUID which is in-phase with the voltage response of each other SQUID in the array.