Atoms in wells with predominantly σ⁺ (σ^-) polarized light, labeled σ⁺ (σ^-) wells in Fig. 10a, are predominantly in the m = +F (m = -F) state. To initiate observable tunneling between the σ^- and σ⁺ wells of the lattice, the repumping laser is turned off, and a σ⁺ polarized laser (colinear with the lattice beams and resonant with the D2, F→2 to F'→2 transition) is turned on for a short time. This laser pulse (magnetizer) removes most atoms from the σ^- lattice wells by optical pumping into the F = 1 ground state, whereas the atoms in the σ⁺ wells survive (Fig. 10b).

A tunneling event (Fig. 10c) from a σ⁺ well into a σ^- well is associated with an exchange of 4ħ angular momentum between the atom and the lattice field, amounting to an exchange of two photon pairs between the σ⁺ and σ^- components of the lattice beams. Thus, using the fact that all ~10⁶ atoms in the lattice tunnel in phase, we can measure the tunneling current by separating the lattice beams after their interaction with the atoms into their σ-polarized components, and measure the difference of the intensities of the σ⁺ and σ^- components.