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.
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