  In this article the effect of noise on Grover's algorithm is analyzed,
modeled as a total depolarizing channel (TDCh) and a local depolarizing channel
in each qubit (LDCh). The focus was not in error correction (e.g. by the
fault-tolerant method), but to provide an insight to the kind of error, or
degradation, that needs to be corrected. In the last years analytical results
regarding mainly the TDCh model have been obtained. In this paper we extend
these previous results to the local case, concluding that the degradation of
Grover's algorithm with the latter is worse than the former. It has been shown
that for both cases with an $N$-dependent small enough error-width, smaller
than $1/\sqrt{N}$ for total error and $1/(\sqrt{N}\log_2{N})$ for the local
case, correction is not needed.
