Improvement of average magnetic field measurement based on magnetic-field-sensitive Ramsey fringes.

Accurate magnetic field measurement is the key to evaluating the second-order Zeeman effect. The conventional method is to deduce the magnetic field by determining the center frequency of the magnetic-field-sensitive Ramsey fringes. In this Letter, we present a more rigorous theory for this method and demonstrate that the current peak-searching method has a non-negligible sub-Hz or even larger deviation. We introduce an improved method that considers more parameters and a strict formula that can correct the deviation and suppress it to below 0.1 Hz. Corresponding experiments on the Rb atomic fountain demonstrate that this improved method is expected to enhance the precision of magnetic field measurement and improve the atomic fountain clock.