A novel method for detecting the gradient of a magnetic field uses an elongated cloud of cesium atoms cooled near the absolute zero. Since the rotation of atomic spins depends on the magnetic field, an image of the spin states can be used to measure how the magnetic field changes along the cloud. The gradient is determined from a single image, which is an advantage over standard methods where multiple images are needed.
The article is available at Phys. Rev. A 103, 022611, and arXiv:2011.09779.