# quantum theory

- any theory predating quantum mechanics that encompassed Planck's radiation formula and a scheme for obtaining discrete energy states for atoms, as Bohr theory.
- any theory that treats certain phenomena by the methods of quantum mechanics: a quantum theory of gravitation.

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## Origin of quantum theory^{}

First recorded in 1910–15

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

## quantum theory

- a theory concerning the behaviour of physical systems based on Planck's idea that they can only possess certain properties, such as energy and angular momentum, in discrete amounts (quanta). The theory later developed in several equivalent mathematical forms based on De Broglie's theory and on the Heisenberg uncertainty principleSee wave mechanics

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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

## quantum theory

- See quantum mechanics.
- Any of various theories that makes use of the assumptions, principles, and laws of quantum mechanics.

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The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.