  Quantum random walk finds application in efficient quantum algorithms as well
as in quantum network theory. Here we study the mixing time of a discrete
quantum walk over a square lattice in presence percolation and decoherence. We
consider bit-flip and phase damping noise, and evaluate the instantaneous
mixing time for both the cases. Using numerical analysis we show that in case
of phase damping noise probability distribution of walker's position is
sufficiently close to the uniform distribution after infinite time. However,
during the action of bit-flip noise, even after infinite time the total
variation distance between the two probability distributions is large enough.
