Jordan, Ernst Pascual (1902-1980) was a German physicist and one of the founders of the science of quantum mechanics, along with Max Born and Werner Heisenberg. With Wolfgang Pauli, Oskar Klein, and Eugene Paul Wigner, he later developed the theory of quantum electrodynamics.

Jordan received his Ph.D. degree in physics in 1924 from the University of Göttingen, where he was influenced by Niels Bohr and became physicist Max Born's most important collaborator in his work to establish a new and more rational basis for quantum theory.

Leaving Göttingen, Jordan went to the University of Rostock in 1929. He was appointed professor of physics there in 1935 and thereafter served as professor of theoretical physics at both the University of Berlin (1944-1952) and the University of Hamburg (1951-1970).

Jordan's key contribution to quantum theory was to take Austrian physicist Erwin Schrödinger 's wave equation, which expressed the dual wave-particle nature of matter, and reexpress it in a so-called “matrix” formulation. The matrix formulation expresses the fundamental physical quantities as rectangular arrays of numbers—called operators—instead of waves. While it is mathematically equivalent to the wave equation and gives the same answers for the properties of atoms, the matrix approach was easier to use for calculations and gave physicists an alternative picture, which greatly expanded their understanding of the new and mysterious world of the uncertainty principle.

Despite all of Jordan's exceptional scientific contributions, for which he received both the Max Planck and Gauss Medals, he was perceived to have been politically involved with the Nazis during the reign of Adolf Hitler, and during World War II (1939-1945) was part of the Luftwaffe meteorological staff in Hamburg-Fulsbuttel. After the war, he was eventually reinstated as a full professor at Hamburg, but this did not occur until 1953.