  Optical tweezers have become essential tools to manipulate atoms or molecules
at a single particle level. However, using standard diffracted-limited optical
systems, the transverse size of the trap is lower bounded by the optical
wavelength, limiting the application range of optical tweezers. Here we report
trapping of single ultracold atom in an optical trap that can be continuously
tuned from a standard Airy focus to a subwavelength hotspot smaller than the
usual Abbe's diffraction limit. The hotspot was generated using the effect of
superoscillations, by the precise interference of multiple free-space coherent
waves. We argue that superoscillatory trapping and continuous potential tuning
offer not only a way to generate compact and tenable ensembles of trapped atoms
for quantum simulators but will also be useful in single molecule quantum
chemistry and the study of cooperative atom-photon interaction within
subwavelength arrays of quantum emitters.
