Quantum fields are fundamental entities in quantum field theory, a framework used to describe and understand the behavior of particles and their interactions in quantum physics. They are not made of anything else but are considered fundamental building blocks themselves.
According to current theories, such as the Standard Model of particle physics, quantum fields permeate all of space and are responsible for the creation and annihilation of particles. Every elementary particle, such as electrons, quarks, and photons, is associated with its own unique quantum field. These fields are described by mathematical equations and are quantized, meaning they can exist in discrete, quantized energy states.
The concept of quantum fields emerged with the development of quantum field theory in the early to mid-20th century. The groundwork for quantum field theory was laid down by several physicists, including Albert Einstein, Max Planck, Werner Heisenberg, and Paul Dirac. However, it was the work of pioneers such as Richard Feynman, Julian Schwinger, and Sin-Itiro Tomonaga in the late 1940s that provided a complete and consistent mathematical framework for quantum field theory.
The field concept in quantum field theory allows for a unified description of particles and their interactions. It treats particles as excitations or disturbances in their corresponding quantum fields. These disturbances propagate through space and time, and their interactions are mediated by the exchange of other particles. For example, the electromagnetic force between charged particles is described by the exchange of virtual photons, which arise from the interaction of the electron and photon quantum fields.
Quantum field theory, with its fundamental quantum fields, has been remarkably successful in describing and predicting the behavior of elementary particles and their interactions. It is a cornerstone of modern particle physics and has been confirmed by numerous experimental observations.