  Quantum computers are susceptible to noises from the outside world. We
investigate the effect of perturbation on the hitting time of a quantum walk
and the stationary distribution prepared by a quantum walk based algorithm. The
perturbation comes from quantizing a transition matrix Q with perturbation E
(errors). We bound the perturbed quantum walk hitting time from above by
applying Szegedy's work and the perturbation bounds with Weyl's perturbation
theorem on classical matrix. Based on an efficient quantum sample preparation
approach invented in {\em speed-up via quantum sampling} and the perturbation
bounds for stationary distribution for classical matrix, we find an upper bound
for the total variation distance between the prepared quantum sample and the
true quantum sample.
