  We prove the spectral gap property for random walks on the product of two
non-locally isomorphic analytic real or p-adic compact groups with simple Lie
algebras, under the necessary condition that the marginals posses a spectral
gap. Furthermore, we give additional control on the spectral gap depending on
certain specific properties of the given groups and marginals; in particular,
we prove some new cases of the super-approximation conjecture. One ingredient
of the proof is a local Ulam stability result which is introduced and proved in
this paper. This result characterizes partially defined almost homomorphisms
between two analytic compact groups with simple Lie algebras.
