Rubidium atoms are loaded into and trapped within a hollow-core photonic crystal fiber. A cross section of the hollow fiber is shown in the upper right. A dipole trapping beam (large red arrow) serves to localize the atoms (red, not drawn to scale) within the hollow core of the fiber. Additional probe, coupling, and switch fields (red, green, and blue wave packets, respectively) can then control the atomic state and implement all-optical switching and electromagnetically induced transparency. The relevant atomic levels are indicated as states , , , and in the upper left. Note: the actual experimental orientation of the fiber is vertical to enable loading from a magneto-optical trap (not shown).