  Localization of single fluorescent molecules is key for physicochemical and
biophysical measurements such as single-molecule tracking and super-resolution
imaging by single-molecule localization microscopy (SMLM). Recently a series of
methods have been developed in which the localization precision is enhanced by
interrogating the molecular position with a sequence of spatially modulated
patterns of light. Among them, the MINFLUX technique outstands for achieving a
~10-fold improvement compared to wide-field camera-based single-molecule
localization, reaching ~1-2 nm localization precision at moderate photon
counts. Here, we present a common mathematical framework for this type of
measurement that allows a fair comparison between reported methods and
facilitates the design and evaluation of new methods. With it, we benchmark all
reported methods for single-molecule localization using sequential structured
illumination, including long-established methods such as orbital tracking,
along with two new proposed methods: orbital tracking and raster scanning with
a minimum of intensity.
