  We consider a quantized version of the Sinai-Derrida model for "random walk
in random environment". The model is defined in terms of a Lindblad master
equation. For a ring geometry (a chain with periodic boundary condition) it
features a delocalization-transition as the bias in increased beyond a critical
value, indicating that the relaxation becomes under-damped. Counter
intuitively, the effective disorder is enhanced due to coherent hopping. We
analyze in detail this enhancement and its dependence on the model parameters.
The non-monotonic dependence of the Lindbladian spectrum on the rate of the
coherent transitions is highlighted.
