PicoTesla absolute field readings with a hybrid 3 He/ 87 Rb magnetometer

We demonstrate the use of a hybrid 3 He/ 87 magnetometer to measure absolute magnetic fields in the pT range. The measurements were undertaken by probing time-dependent 3 He magnetisation using 87 Rb zero-field magnetometers. Measurements were taken to demonstrate the use of the magnetometer in cancelling residual fields within a magnetic shield. It was shown that the absolute field could be reduced to the 10 pT level by using field readings from the magnetometer. Furthermore, the hybrid magnetometer was shown to be applicable for the reduction of gradient fields by optimising the effective 3 He T 2 time. This procedure represents a convenient and consistent way to provide a near zero magnetic field environment which can be potentially used as a base for generating desired magnetic field configurations for use in precision measurements. Graphical abstract