Coherent transport of atomic wavefunctions in modulated optical lattices

Vlad Ivanov
UW Physics

Cold atoms tapped in vertical optical lattices give rise to localized states, the Wannier-Stark states. Delocalization can be recovered by introducing a resonant coupling among neighboring lattice sites. We demonstrated this by applying a modulation either to the phase or the amplitude of the lattice potential. Atomic sample loaded into a modulated vertical optical-lattice potential exhibit a resonant delocalization dynamics arising from intraband transitions among Wannier-Stark levels. Wannier-Stark intraband transitions are observed by monitoring the in situ atomic sample extent. By varying the modulation frequency, we find resonances at integer multiples of the Bloch frequency and the resonances show a Fourier-limited width for modulation times up to 15 s. Under non-resonant driving of the lattice phase we coherently control the spatial extent of the wavefunction by reversibly stretching and shrinking the wavefunction over a millimeter distance. We demonstrate the ability to reversibly switch between localized and delocalized state. Furthermore we found that the resonant tunneling process at the basis of the Wannier-Stark intraband transitions can be used to determine the gravity acceleration with sub-ppm sensitivity and sub-millimeter spatial resolution.