Paul ( P. A. M.) Dirac formulated the most elegant version of the mathematical principles of quantum mechanics after hearing a lecture by Werner Heisenberg on his new ideas of "matrix mechanics." Shortly after matrix mechanics, Erwin Schrödinger developed his "wave mechanics" and showed it was equivalent to the Heisenberg picture. Dirac combined both of these using a method from classical mechanics called Poisson brackets. In his 1930 textbook The Principles of Quantum Mechanics, Paul Dirac introduced the concepts of superposition and indeterminacy using examples with polarized photons. The examples suggest a very simple and inexpensive experiment that we call the Dirac 3-polarizers experiment to demonstrate the notions of quantum states, the preparation of quantum systems in states with known properties, the superposition of states, the measurement of various properties, the projection or representation of a state vector in another basis set of vectors, and the infamous "collapse" or "reduction" of the wave function and the resulting indeterminacy.
For TeachersChapter 1 of The Principles of Quantum Mechanics