Creating and imaging atomic wave functions with diffraction-breaking resolution.
Optical trapping and imaging of atoms plays an essential role in cold-atom physics, ranging from precision measurement to the study of correlated many body systems. Due to the diffraction limit, trapping and imaging are typically limited to length scales on the order of the wavelength of the light. The nonlinear response of three-level atoms, however, supports a dark state with spatial structures much smaller than the wavelength. In this talk, I will present the experimental use of such dark state spatial structure to both create optical potentials and probe the atomic wave function with a resolution of lambda/50, far below the diffraction limit. The optical potential physically realizes a Kronig-Penney lattice of near delta-function barriers with widths below 10nm. The coherent nature of our approach also provides a fast temporal resolution (500 ns), with which we could observe the quantum motion of atoms inside the unit cell of an optical lattice.
 arXiv: 1807.02871
 PRL 120, 083601 (2018)