  We investigate the electronic Bloch oscillation in bilayer graphene gradient
superlattices using transfer matrix method. By introducing two kinds of
gradient potentials of square barriers along electrons propagation direction,
we find that Bloch oscillations up to terahertz can occur. Wannier-Stark
ladders, as the counterpart of Bloch oscillation, are obtained as a series of
equidistant transmission peaks, and the localization of the electronic wave
function is also signature of Bloch oscillation. Forthermore, the period of
Bloch oscillation decreases linearly with increasing gradient of barrier
potentials.
