Illustration: Alan Stonebraker.

Figure 1: 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 $|g〉↔|e〉$.