Conceptual

Vacuum-Induced Atomic Grating in Cavity Quantum Optics

A fully quantum version of electromagnetically induced grating in which the control field driving a three-level atomic ensemble is not a classical standing wave but the quantized field of an optical cavity - even its vacuum state. Students learn how the vacuum and few-photon states of a strongly coupled cavity spatially modulate a probe field so the cold-atom medium diffracts it into zeroth- and first-order peaks, how the first-order intensity rises then falls with cavity photon number, and how the on-resonance first-order peak turns into a dip with side peaks as photons increase - a signature that can distinguish the quantum state of the cavity field.