Oscillation frequency f BO as a function of the detuning f (dots, top) and the oscillation frequency difference | f BO - f | (dots, bottom) for values extracted from experiments (circles) with simulated results for various levels of dispersion (lines). The oscillation frequencies were extracted as the peaks of the Fourier transform of the evolution of the participation ratio over time. The error bars denote the width of a peak at 1% height reduction. The oscillation frequency deviates from the modulation frequency for small detuning values due to increasing dispersion in the Wannier-Stark ladder that stems from the quadratic potential. Here r D denotes the ratio between the dispersion value we used in each case and the experimentally retrieved value. Bright colours indicate < c , and dark colours > c.
