Progress toward a zero-magnetic-field environment for ultracold-atom experiments

The minimization of the magnetic field plays a crucial role in ultracold gas research. For instance, the contact interaction dominates all the other energy scales in the zero-magnetic-field limit, giving rise to novel quantum phases of matter. However, lowering magnetic fields well below the mG level is often challenging in ultracold gas experiments. In this paper, we apply Landau-Zener spectroscopy to characterize and reduce the magnetic field on an ultracold gas of sodium atoms to a few tens of $\mu G$. The lowest magnetic field achieved here opens the way to observing novel phases of matter with ultracold spinor Bose gases.