Hello! Im trying to do QFT on my own and its going fine.. except one confusion now. We have our operator fields corresponding to our observables, and our state which is a function of space and time. But doing the second quantization we get the creation and destruction operators which now take the place in the Klein-Gordon solution that our coefficients a(k) and a^(+)(k) for the planewaves use to have. So the Klein-Gordon solution is not our state but an operator field? Edit: Maybe I got it now. generalizing a(k) and a^(+)(k) to operators the KG solution gives the general form of a operator that when acting on |0> gives a wavefuntion solution?