  Quantum simulations of Hubbard models with ultracold atoms rely on the
exceptional control of coherent motion provided by optical lattices. Here we
demonstrate enhanced tunability using an optical superlattice in a fermionic
quantum gas microscope. With our phase-stable bichromatic design, we achieve a
precise control of tunneling and tilt throughout the lattice, as evidenced by
long-lived coherent double-well oscillations and next-nearest-neighbor quantum
walks in a staggered configuration. We furthermore present correlated quantum
walks of two particles initiated through a resonant pair-breaking mechanism.
Finally, we engineer tunable spin couplings through local offsets and create a
spin ladder with ferromagnetic and antiferromagnetic couplings along the rungs
and legs, respectively. Our work underscores the high potential of optical
superlattices for engineering, simulating, and detecting strongly correlated
many-body quantum states.
