**Quantum electrodynamics** (**QED**) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons and represents the quantum counterpart of classical electromagnetism giving a complete account of matter and light interaction. One of the founding fathers of QED, Richard Feynman, has called it "the jewel of physics" for its extremely accurate predictions of quantities like the anomalous magnetic moment of the electron, and the Lamb shift of the energy levels of hydrogen.

In technical terms, QED can be described as a perturbation theory of the electromagnetic quantum vacuum.

Read more about Quantum Electrodynamics: History, Mathematics, Renormalizability, Nonconvergence of Series

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### Famous quotes containing the word quantum:

“But how is one to make a scientist understand that there is something unalterably deranged about differential calculus, *quantum* theory, or the obscene and so inanely liturgical ordeals of the precession of the equinoxes.”

—Antonin Artaud (1896–1948)