A physical interpretation of product operator terms

A visual development of the product operator formalism is attempted in this article; the aim being to present in a straightforward pictorial manner, the physical meaning of various product operator terms and how they transform under radiofrequency pulses and delays. The density operator approach along with the quantum mechanics needed to understand it is introduced later to justify the visual development given at the beginning of the article. Greenberger-Horne-Zeilinger (GHZ) entangled particles are discussed from the perspective of spin-half nuclei for the sole purpose of showing that things are not so simple after all and that a visual approach will have its limits. Nevertheless, the visual approach presented here may provide some assistance in the understanding of this important formalism.