I take the view that quantum field theory (QFT) can be extended to quantum field theory (QFT) because I believe that quantum mechanics (QM) is easier to understand.
So imagine that there are a number of stretching bed sheets that lie on top of each other.
Each of these sheets is a ‘field’, and it can swing.The sheets can all swing independently of each other, but they sometimes touch each other.
Of course, our sheets are infinitely large, and can swing through.Magical quantum field sheets, then.
Really interacting with each other they do only when the humpbacks hit exactly another sheet while swinging.
When this happens, we observe an ‘event’, i.e. the exchange of vibrational force from one sheet to another.
The “quantum” in the whole thing describes that the sheets are located at very specific distances to each other, and the interactions therefore only take place at certain distances.So two sheets, which are far apart, would have to swing very doll to interact directly with each other.
Some of these sheets vibrate on the strengths of the world.This is what we call “energy levels”.
The individual sheets represent a type of ‘particle’.I put this in goosebumps, because actually these particles do not exist, it is only the wave mountains in the vibrations of the sheets, which we had long misunderstood as little ‘things’.
But this is also understandable, after all, our normal perception works on the basis of things, and for many years physics has been concerned with things and their mechanics.
Quantum mechanics also describes things, but allows them to be ‘waves’ until they are ‘observed’.This generally means ‘until they interact with another wave, or themselves’.
This seemed very mysterious and counterintuitive.Almost eerie, since it could lead, among other things, to interactions that, in a classical lyrised way, could be handled faster than light, namely immediately, over unlimited distances.
The crux of the matter was that one could not determine the exact location of a ‘particle’, and in principle not its exact velocity, and so on.Instead, you could only have one mix of these characteristics, and the more accurately you wanted to measure one, the more inaccurate the others were.
And so it was decided that these things should be given only as probabilities.The explanation with the vibrating sheets instead of individual ‘particles’ was not yet available.
So it was still thought that every photon, every electron, and so on, separate from each other, actually ‘exists’, so in the classical sense, even if it could not be measured exactly, in only one place, only one speed, has, etc.
So it was assumed that the ‘wave’ was not real, but the best approximation to the actual reality of the particle, and when it actually interacted with another particle, they found out where it really was.
However, this is problematic if this ‘particle’ should have been in several places at once, because it has ‘interfered’ with itself.
Interfering is something that waves do, not particles.So it was assumed that the ‘particles’ between their interactions only ‘existed’ as a wave – a particle, a wave.
This “wave” describes the probability with which, if you try to measure it, you would find the particle.
So it was assumed that the ‘particle’ takes all possible paths, and when you find it, all versions disappear except the one you found.
This results in the infamous “path integtal” of quantum mechanics.
In quantum field theory, we assume instead that a ‘particle’ is everywhere, but more here than there, and every time it is ‘observed’, i.e. the sheets touch exactly when swinging, then this changes the course of the vibration in the sheets.
In fact, there are no ‘particles’ at all, but only interacting energy levels in the fields that move wave-like through the fields.