  We study numerically the expansion dynamics of an initially confined quantum
wave packet in the presence of a disordered potential and a uniform bias force.
For white-noise disorder, we find that the wave packet develops asymmetric
algebraic tails for any ratio of the force to the disorder strength. The
exponent of the algebraic tails decays smoothly with that ratio and no evidence
of a critical behavior on the wave density profile is found. Algebraic
localization features a series of critical values of the force-to-disorder
strength where the m-th position moment of the wave packet diverges. Below the
critical value for the m-th moment, we find fair agreement between the
asymptotic long-time value of the m-th moment and the predictions of
diagrammatic calculations. Above it, we find that the m-th moment grows
algebraically in time. For correlated disorder, we find evidence of systematic
delocalization, irrespective to the model of disorder. More precisely, we find
a two-step dynamics, where both the center-of-mass position and the width of
the wave packet show transient localization, similar to the white-noise case,
at short time and delocalization at sufficiently long time. This
correlation-induced delocalization is interpreted as due to the decrease of the
effective de Broglie wave length, which lowers the effective strength of the
disorder in the presence of finite-range correlations.
