Quantum mechanics is general name given to modern theories of sub-atomic matter. Rather than matter being seen as simple substance in space -- as in the model of the atom as a set of electrons spinning around a central nucleus -- quantum mechanics treats matter in terms of what we can actually know about such entities: there are in certain places at certain times quanta of energy which we can measure and map in terms of mathematical matrices. The first theorisation of quanta is found in Albert Einstein's seminal papers of 1905 (q.v.). Other notable contributors to the development of the theory were Max Planck, Niels Bohr and Werner Heisenberg (q.v.)
Editors. "Quantum Mechanics". The Literary Encyclopedia. First published 28 October 2000; last revised 30 November -1.
[http://www.litencyc.com/php/stopics.php?rec=true&UID=914, accessed 28 April 2015.]