  The use of a dynamic "accordion" lattice with ultracold atoms is
demonstrated. Ultracold atoms of $^{87}$Rb are trapped in a two-dimensional
optical lattice, and the spacing of the lattice is then increased in both
directions from 2.2 to 5.5 microns. Atoms remain bound for expansion times as
short as a few milliseconds, and the experimentally measured minimum ramp time
is found to agree well with numerical calculations. This technique allows an
experiment such as quantum simulations to be performed with a lattice spacing
smaller than the resolution limit of the imaging system, while allowing imaging
of the atoms at individual lattice sites by subsequent expansion of the optical
lattice.
