One layer of a regular array of independent one-dimensional chains of ultracold bosonic atoms created by an optical lattice. The two Bragg pulses are also displayed (blue and green arrows). The inset shows an atom absorbing a photon from the first laser beam followed by stimulated emission into the second beam. This process transfers momentum ħq and energy ħν to the atom cloud. Spontaneous emission Γ is suppressed by a large detuning Δ from the atomic transition |g〉↔|e〉.