Quantum Field Theory (QFT) is a theoretical framework that combines classical field theory, special relativity, and quantum mechanics.
- Quantum fields are thought to be the underlying reality of all particles and forces. Quantum field theory has developed the Standard Model to describe all the known fundamental particles and force carriers as fields.
- Quantum field theory uses mathematical formulas to represent things that are often too small or transient to observe. The exact behaviour of forces, particles and waves can often only be inferred and so must be described in terms of a mathematical probability of different events and outcomes.
- Quantum fields serve as the comprehensive framework that encompasses the entirety of matter-energy and can be thought of as a dynamic medium that permeates all of space. It is a unified theory of spacetime and matter in which particles are simply localized excitations of this medium. This means that when a particle appears, it is a localized disturbance in a quantum field. When a particle is destroyed, the disturbance in the quantum field disappears.
- In quantum field theory, a quantum field is an entity whose fundamental element is a “quantum” of energy. A quantum of energy is the smallest possible unit quantity that can be contained within a field. This is the smallest possible unit that can be used to describe the behaviour of the quantum field in question.
- So, a quantum field can be thought of as a field that may be made up of a single quantum of vibrating matter-energy – a particle. However, a quantum field can include more than one unit. The number of particles in a quantum field is determined by the state of the field so can be between zero to an infinity of quanta.
- A field containing a single particle and a field containing groups of particles are related in the sense that they are both manifestations of the same underlying quantum field. The difference is that the field containing a single quantum is a localized disturbance, while the field containing groups of particles is more spread out (diffuse).
- The electromagnetic field (EM field) is an example of a quantum field. Disturbances in the EM field create photons. Photons are responsible for all forms of electromagnetic radiation from radio waves through visible light to gamma rays. It is also responsible for the force of electromagnetism, which is one of the four fundamental forces of nature.