PG cooling is typically performed using a 3D optical setup with three pairs of perpendicular laser beams with an atomic ensemble in the center. Each beam is prepared with an orthogonal polarization to its counterpropagating beam. The laser frequency detuned from a selected transition between the ground and excited states of the atom. Since the cooling processes rely on multiple transitions between care must be taken such that the atomic does not fall out of these two states. This is done by using a second, "repumping", laser to pump any atoms that fall out back into the ground state of the transition. For example: in cesium cooling experiments, the cooling laser is typically chosen to be detuned from the | 6 2 S 1 / 2 F = 4 ⟩ ⟩ to | 6 2 P 3 / 2 F ′ = 5 ⟩ ⟩ transition and a repumping laser tuned to the | 6 2 S 1 / 2 F = 3 ⟩ ⟩ to | 6 2 P 3 / 2 F ′ = 4 ⟩ ⟩ transition is also used to prevent the Cs atoms from being pumped into the | 6 2 S 1 / 2 F = 3 ⟩ ⟩ state.