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If Electromagnetic waves are caused due to the vibrations in the electric and mutually perpendicular magnetic fields, and since according to QFT, particles are formed due to the vibrations caused in their respective fields. But which fields produce photons, because the vibrations in electromagnetic fields produce only EM waves?

Note :- I see there is one similar question that states - "How to introduce the electromagnetic field in Quantum Field Theory?" but the explanation as well as the question is totally mathematical, I want a rather simple interpretation of my question.

Ajinkya Naik
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Essentially, photons are the result of a "secondary quantization": that is, they appear when we associate the excitations of the electromagnetic field with particles. So in QFT terms, photons are the excited states of the electromagnetic field. If the e/m field is in the main state (vacuum), there are no photons present.

We might take a different approach and treat them as waves - which is often used in quantum mechanics and quantum optics. In this case, one is dealing with "waves of probability" described by the state vector or density matrix. But this would be just the other description of the same thing. Which one would fit the best, depends on the problem that we're trying to solve. QFT is especially useful for many-particle systems, while wave approach is more about individual photons interacting with something else.

That's my perspective, anyway.

J. Pipiskin
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