What is quantum electrodynamics?

Quantum electrodynamics is the relativistic quantum field theory describing how light and matter interact through electrically charged particles and photons. It is celebrated as the most precise and stringently tested theory in physics, achieving full agreement between quantum mechanics and special relativity. Richard Feynman notably referred to it as the jewel of physics due to its extremely accurate predictions.

What we know

• Quantum electrodynamics is an abelian gauge theory describing the quantum interactions of the electromagnetic field with matter. [1, 2]
• QED is the first theory where full agreement between quantum mechanics and special relativity is achieved. [2]
• Richard Feynman called quantum electrodynamics the jewel of physics for its extremely accurate predictions. [2]
• The theory mathematically describes all phenomena involving electrically charged particles interacting by means of exchanging photons. [2]

Still open

• The prediction of vacuum zero energy made by QED has a 10^120 magnitude difference compared to experimental observation values, known as the cosmological constant problem or vacuum catastrophe.

Where to go next

• how it workedHow does cavity QED study light-matter interaction?
• a case in pointWhat is circuit quantum electrodynamics?
• compared withWhat is stochastic electrodynamics?
• the bigger pictureHow does special relativity combine with quantum mechanics?
• what followedWhat is the cosmological constant problem?
• an unexpected connectionHow does cavity QED relate to quantum computers?Cavity quantum electrodynamics can be used to construct a quantum computer by swapping atomic qubit states onto cavity fields.

Sources

• [1]quantum electrodynamics (Wikidata Q234881) · CC0 1.0
• [2]Quantum electrodynamics · CC BY-SA 4.0
• [3]Cavity quantum electrodynamics · CC BY-SA 4.0
• [4]Circuit quantum electrodynamics · CC BY-SA 4.0
• [5]Stochastic electrodynamics · CC BY-SA 4.0