Abstract

In November of 1925 Born, Heisenberg and Jordan wrote an article together in which they demonstrated that Einstein's energy fluctuation formula could be derived from quantum mechanics. They remark that the equations are subject to reinterpretation. Specifically, the states of radiation oscillators can be reinterpreted as numbers of quanta of radiation. They also connected this latter idea up with Bose-Einstein statistics. Heisenberg wrote to Pauli that it was Jordan who contributed the idea of reinterpreting the terms. This was the first step toward quantum field theory. In August of the following year Dirac derived Einstein's A and B coefficients for induced transitions between states but on the assumption that the electromagnetic field could be treated classically (Dirac 1927). In 1927 Dirac lay the mathematical foundations for quantum electrodynamics. Early that year he combined quantum mechanics, special relativity, and radiation theory in treating the electromagnetic field as if it were an infinite collection of oscillators.