Fig. 3: Sensitivity and frequency response of the weak measurement resonance magnetometer.

a The sensitivity spectrum derived from the g⁽²⁾(0) noise spectrum divided by the “resonance slope vs. frequency” curve, or the response curve. The former was generated by a fast Fourier transform of 30,300 continuous data points of g⁽²⁾(0) values measured at g⁽²⁾(0) ~ 0, within 10 s, with each data point obtained from the time duration of one modulation period. b The normalized g⁽²⁾(0) resonance slope measured at g⁽²⁾(0) ~ 0 for different AC magnetic field frequencies, with respect to the slope measured for a DC magnetic field. The fitting curve follows the function \({\mathrm{BW}}/\sqrt {{\mathrm{BW}}^2 + f^2}\) with BW = 16 Hz. Experimental parameters: the total input laser power of 15 µW and D = 0.995. The test DC field we applied is 0.1 nT for assessing the magnetometer sensitivity. The magnitude of the oscillating magnetic field for measuring the atomic frequency response is 3.9 pT.