  We study a semiclassical random walk with respect to a probability measure
with a finite number n_0 of wells. We show that the associated operator has
exactly n_0 exponentially close to 1 eigenvalues (in the semiclassical sense),
and that the other are O(h) away from 1. We also give an asymptotic of these
small eigenvalues. The key ingredient in our approach is a general
factorization result of pseudodifferential operators, which allows us to use
recent results on the Witten Laplacian.
