I need someone to point me towards an instance of a relatively simple QFT problem which illustrates what can be calculated from QFT, how it is calculated, and its physical significance. (Note the qualification "relative". I realize there are likely no simple problems in QFT.) If someone were asking the same of me with regard to QM, I would take them to the standard examples in the texts: The potential well, the step-potential barrier, the harmonic oscillator and the ideal hydrogen model. If I were to single one out it would probably be the step-potential barrier, since it illustrates how a boundary value problem is solved and clearly gives two or more distinct relative probability regions while also exhibiting a non-classical behavior: "tunnelling". I would also bring up the two-slit experiment since one can discuss all the quantum behaviors and easily visualize the significance of both amplitude and phase--without actually solving the math. What QFT problem(s) can do this for beginner? Edit: It should clarify the physical significance of a quantum field and (if possible) show how it is related to the physical entities we call particles.