Table of Contents

- 1 What is quantum field theory in simple words?
- 2 What is a particles quantum state?
- 3 What are superposition states in quantum physics?
- 4 Are quantum particles everywhere?
- 5 How is superposition measured?
- 6 Are entangled particles in superposition?
- 7 What is QFT (quantum field theory)?
- 8 When do particles become something when they are observed?

## What is quantum field theory in simple words?

Definition of quantum field theory : a theory in physics: the interaction of two separate physical systems (such as particles) is attributed to a field that extends from one to the other and is manifested in a particle exchange between the two systems.

## What is a particles quantum state?

A sub-microscopic system (a sub-atomic particle or set of sub-atomic particles moving under a force field or exerting a force on each other) is described by a “quantum state” (or just “state”) which is a list of physical properties of the system that can be measured simultaneously.

**What is a particle field?**

In quantum field theory, force carriers or messenger particles or intermediate particles are particles that give rise to forces between other particles. These particles are bundles of energy (quanta) of a particular kind of field. There is one kind of field for every type of elementary particle.

### What are superposition states in quantum physics?

The principle of quantum superposition states that if a physical system may be in one of many configurations—arrangements of particles or fields—then the most general state is a combination of all of these possibilities, where the amount in each configuration is specified by a complex number.

### Are quantum particles everywhere?

Up until this point, we’ve been thinking of fields in terms of empty space: the quantum fields we’re discussing exist everywhere. But particles don’t exist everywhere at once. On the contrary, they’re what we call localized, or confined to a particular region of space.

**What is the particle theory?**

The kinetic theory of matter (particle theory) says that all matter consists of many, very small particles which are constantly moving or in a continual state of motion. The degree to which the particles move is determined by the amount of energy they have and their relationship to other particles.

## How is superposition measured?

The linear combination of two or more eigenstates results in quantum superposition of two or more values of the quantity. If the quantity is measured, the value of the physical quantity will be random, with a probability equal to the square of the coefficient of the superposition in the linear combination.

## Are entangled particles in superposition?

As pointed out above, superposition is necesary for entanglement, but they are not the same. On a formal level, superposition is just the sum of vectors in a Hilbert space.

**What is a quantum field?**

What we interpret as “matter” is itself a quantum field. And these quantum fields are made up of particles. Quantum field theory (QFT) is the concept that the universe is an entanglement of energy waves. QFT was first theorized by Albert Einstein, Werner Heisenberg, and Max Planck. What we perceive as particles are excitations of the quantum field.

### What is QFT (quantum field theory)?

Quantum Field Theory (QFT) is the mathematical and conceptual framework for contemporary elementary particle physics. In a rather informal sense QFT is the extension of quantum mechanics (QM), dealing with particles, over to fields, i.e. systems with an infinite number of degrees of freedom.

### When do particles become something when they are observed?

Therefore, particles are in a state of potential until they are observed. They become something when observed. When this ‘observer effect’ was first noticed by the early pioneers of quantum theory, they were alarmed.

**Can QM describe a system with a variable number of particles?**

Neither QM nor its immediate relativistic extension with the Klein-Gordon and Dirac equations can describe systems with a variable number of particles. However, obviously this is essential for a theory that is supposed to describe scattering processes, where particles of one kind are destroyed while others are created.