In this report we present preliminary results about the tunneling problem for a magnetic Schrödinger operator. As a motivation we consider the 3-D time-dependent Schrödinger operatorwhere V is a radial potential and E(t) a circularly polarized field with uniform frequency ω.The quantum monodromy operator (QMO) that takes the system through a complete period T = 2π/ω, turns out to be unitarily equivalent to e iT P A (x,hDx)/h , where P A (x, hDx)) identifies with a magnetic Schrödinger operator. When V is sufficiently confining, P A (x, hDx)) presents a double magnetic well. Then we construct its semi-classical ground state and examine the splitting between its two first eigenvalues.