Quantum optics is a field of research in physics, dealing with the application of quantum mechanics to phenomena involving light and its interactions with matter.
Light is made up of particles called photons and hence inherently is “grainy” (quantized). Quantum optics is the study of the nature and effects of light as quantized photons.
Research into quantum optics that aims to bring photons into use for information transfer and computation is now often called photonics to emphasize the claim that photons and photonics will take the role that electrons and electronics now have.
— Wikipedia on Quantum optics
2009.12.17 Thursday ACHK