What is Quantum Field Theory?
Quantum field theory is the study of physics on an atomic and subatomic level. It's an explanation of particle physics that shows how all forces in the universe can be unified under one main force. If you understand quantum field theory, you can master the four fundamental forces in the universe; electromagnetism, gravity, and the strong and weak nuclear forces. In this article, we'll take a look at what quantum field theory is and how it works!
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What is Quantum Field Theory
Quantum field theory, or QFT, has been a puzzle for theoretical physicists ever since it was first created. QFT tries to unify quantum mechanics and classical theories of electromagnetism and strong and weak nuclear forces (Nuclear Physics). One way of explaining the unification of these fields by quantum field theory is through perturbation. Perturbations can be seen as small disturbances to a system. Perturbations describe phenomena on the boundary between classical physics and quantum physics and one consequence of perturbations being important in quantum field theory are that they lead to the uncertainty principle in quantum mechanics. In order to understand how this occurs, consider two particles interacting with each other through an exchange process involving 3 sets of variables: position, momentum and energy (the 4th variable
How did it come about
Quantum field theory was born in an effort to reconcile the apparent contradictions between quantum mechanics and classical field theory. It can be challenging for many people to wrap their heads around this concept but I'm going to attempt a layman's explanation of how it came about. It all started with Max Planck.
In 1900, Planck hypothesized that light wasn't continuous or atomic but instead could only be emitted or absorbed in quanta which were discrete units of energy. This would make sense if light was quantized like particles (but not all scientists agreed). Albert Einstein saw the connection that Planck had with his own theory of relativity.
The Basic Principles of QFT
Quantum field theory, or QFT, is a mathematical approach to understanding physics on the very small scale. It is most commonly applied to describe elementary particles in fields such as quantum electrodynamics and quantum chromodynamics. The field models how the particles interact with each other as well as how these interactions change over time.
Quantum theory tells us that everything in the universe has quantized energy levels (where energy can only take on certain values) and according to QFT it applies not just to electrons and protons but also to photons which are packets of light energy that travel together through space and time. These photons only appear when their associated particle has enough energy for them to exist for a short period of time.
The Copenhagen Interpretation
Quantum field theory, developed by Austrian physicist Wolfgang Pauli and Danish physicist Niels Bohr, explains that an atom emits photons or other particles when electrons jump between orbits. The simplest explanation of how this happens is to use the hydrogen atom as an example. Hydrogen atoms consist of a nucleus with one proton and one electron orbiting around it. The proton carries no charge, but the electron does. In the ground state (or lowest energy level), all orbital electrons are paired up; in other words, there are two orbiting at opposite ends of the atom.
The Heisenberg Uncertainty Principle
This principle can be expressed in layman's terms by the following: we cannot accurately measure the position and momentum of a particle at the same time. The act of measuring one parameter affects, to some degree, our ability to measure another. In other words, quantum physics theories tell us that it isn't possible to accurately predict both the position and momentum of a particle at any given time. This is because you'll always have a margin of error that depends on your measurement method.
Instead, according to Heisenberg's Uncertainty Principle, you can only make an educated guess about where it will end up by making an estimate about how much momentum it has based on what type of particle it is and using that data to estimate its path. Know more...