Is the Electromagnetic Field a Classical or Quantum Field?

[dilna]

how we can differentiate classical and quantum fields?i searched everywher..but i did not get a satisfactory answer

 

[maverick_starstrider]

In QFT the fields are operators that obey a commutation relation.

 

[dilna]

electromagnetic field is a classical field or quantum field?in quantum we speak in erms of photons...if we go for second quantisation to electromagnetic field what we will get??

 

[maverick_starstrider]

electromagnetic field is a classical field or quantum field?in quantum we speak in erms of photons...if we go for second quantisation to electromagnetic field what we will get??

Um... there is a Lagrangian that gives the electromagnetic field, working with this field classically one obtains a classical field theory (Maxwell's equations, etc.), if one instead applies canonical quantization to this Lagrangian one gets a quantum field theory (Quantum Electrodynamics). Second quantization IS quantum field theory, the excitations in this case are photons.