Pascual Jordan and Max Born helped turn the new quantum mechanics into a systematic matrix calculus. In this description, a position operator and a momentum operator generally do not commute; the canonical rule is . The order of multiplication therefore carries physical information, rather than being a notational detail. Their 1925 paper developed the mathematical rules connecting these noncommuting quantities with the dynamics and transition frequencies of quantum systems.[ref]
Zur Quantenmechanik by Max Born and Pascual Jordan. 1925 paper, matrix multiplication and canonical quantum condition
A physicist who developed matrix mechanics and held a professorship in theoretical physics at Hamburg.[ref]
Jordan, Pascual (1902–1980). Bezug zu Hamburg: theoretical physics professor; Lebenslauf: full name and 1902–1980 dates
Portrait of Pascual Jordan
. Unknown photographer; Mondadori Publishers. Public domain (anonymous historical photograph, as declared on Commons). Source and usage information on the linked Wikimedia file page. Source. Articles by others on the same topic
Pascual Jordan (1902–1980) was a prominent German theoretical physicist known for his significant contributions to quantum mechanics and quantum field theory. He is recognized for his work on the formulation of quantum mechanics and for being one of the co-developers of the Jordan–Wigner transformation, which is a method used in quantum statistical mechanics and quantum information theory.
One of the leading figures of the early development of quantum electrodynamics.

