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Mag⁴Health quantum sensors

Our magnetometers are based on atomic physics:

a thermal ensemble of helium-4 atoms is continuously excited by a high-frequency discharge in order to populate the 2³S₁ metastable state which is a spin-one state, sensitive to the magnetic field
the metastable ensemble is prepared in a state with a magnetic moment by optical pumping towards 2³P levels with a laser at 1083.2 nm
two radio-frequency fields at different frequencies (9 and 40 kHz) allow exciting parametric resonances. These resonances yield a direct measurement of the 3 components of the magnetic field on the photodetector, in three spectrally separated ranges with a bandwidth of >2 kHz each

Between the specific features of our magnetometers we can highlight:

room temperature operation, needing no heating or cooling, and dissipating very little power (<20 mW per sensor) thanks to the use of a discharge
a bandwidth of more than 2 kHz for all axis
a sensitivity of 40 fT/Hz^1/2 in single axis operation, which is being strongly improved in our new generation of sensors (with the goal of reaching 20 fT/Hz^1/2)
closed-loop operation, compensating in real time up to 300 nT along each axis of the sensor, allowing for an increased dynamic range, and cancelling spurious inter-axis crosstalks. Actually this dynamic range could be widened much further, as demonstrated in CEA recently by operating a similar magnetometer in Earth field with 70 µT dyamic range (to be published in the Review of Scientific Instruments)
real-time 3 axis measurement, with good accuracy (the specific kind of pumping used yielding no light-shifts which could cause systematic errors)