large tunable range, provide a possible platform for direct tuning of wavelength in optical lattice systems. Continuous control of the periodicity of a one-dimensional optical lattice while maintaining trapped atoms in-situ was first demonstrated in 2005 using a single-axis servo-controlled galvanometer. This "accordion lattice" was able to vary the lattice periodicity from 1.30 to 9.3 μm. More recently, a different method of real-time control of the lattice periodicity was demonstrated, in which the center fringe moved less than 2.7 μm while the lattice periodicity was changed from 0.96 to 11.2 μm. Keeping atoms (or other particles) trapped while changing the lattice periodicity remains to be tested more thoroughly experimentally. Such accordion lattices are useful for controlling ultracold atoms in optical lattices, where small spacing is essential for quantum tunneling, and large spacing enables single-site manipulation and spatially resolved detection. Site-resolved detection of the occupancy of lattice sites of both bosons and fermions within a high tunneling regime is regularly performed in quantum gas microscopes. Principle of operation A basic optical lattice is formed by the interference pattern of two counter-propagating laser beams. The trapping mechanism is via the Stark shift, where off-resonant light causes shifts to an atom's internal structure. The effect of the Stark shift is to create a potential proportional to the intensity. This is the same trapping mechanism as in optical dipole traps (ODTs), with the only major difference being that the intensity of an optical lattice has a much more dramatic spatial variation than a standard ODT. The energy shift to (and thus, the potential experienced by) an electronic ground state is given by second-order time-independent perturbation theory, where the rapid time variation of the lattice potential at optical frequencies has been time-averaged.where are the transition matrix elements for transitions from the ground state to the excited states . For a two-level system, this simplifies towhere is the linewidth of the excited state transition. An alternative picture of the stimulated light forces due to the AC Stark effect is to view the process as a stimulated Raman process, where the atom redistributes photons between the counterpropagating laser beams which form the lattice. In this picture, it is clearer that the atoms can only acquire momentum from the lattice in units of , where is the momentum of a photon of one laser beam. Technical challenges The trapping potential experienced by atoms in an optical dipole trap