Richard P. Feynman Quotes
It is to be emphasized that no matter how many [amplitude] arrows we draw, add, or multiply, our objective is to calculate a single final arrow for the event . Mistakes are often made by physics students at first because they do not keep this important point in mind. They work for so long analyzing events involving a single photon that they begin to think that the arrow is somehow associated with the photon [rather than with the event].
Feynman, Richard P. QED: The Strange Theory of Light and Matter. Princeton University Press, 1985, p. 73.
Richard Phillips Feynman was an American theoretical physicist and Nobel Prize winner who made significant contributions to quantum mechanics, quantum electrodynamics, and particle physics. He's known for his work on the Manhattan Project, developing Feynman diagrams, and explaining the interactions between light and matter. While studying for his PhD, Feynman participated in the Manhattan Project and helped develop the atomic bomb. For contributions to the development of quantum electrodynamics, Feynman received the Nobel Prize in Physics in 1965 jointly with Julian Schwinger and Shin'ichirō Tomonaga.