Phys. Rev. X 9, 021001 (2019)

Mapping atomic density with high spatial resolution is of importance for probing many-body effects in cold atomic and molecular systems. Mickey McDonald and co-workers from the US have now performed one-dimensional super-resolution imaging of ultracold atoms with a resolution of 32 nm (full-width at half-maximum) and a localization precision below 500 pm. The experiments involved cold caesium atoms trapped in a one-dimensional optical trapping lattice created by a standing-wave pattern from an infrared laser. An optical pumping lattice with a similar lattice constant is used to pump the atoms from the ground state to a different hyperfine state. Only atoms within a narrow window around the nodes of the optical pumping lattice, where the intensity vanishes, remain in the initial state. By sweeping the location of this window across the lattice and measuring the fraction of atoms in the unexcited state, the atomic density distribution can be mapped with a resolution given by the width of the window, which can be much smaller than the optical wavelength.