quantum theory

American  

[kwon-tuhm thee-uh-ree, theer-ee] / ˈkwɒn təm ˌθi ə ri, ˌθɪər i /

noun

Physics.

1. any theory predating quantum mechanics that encompassed Planck's radiation law and a scheme for obtaining discrete energy states for atoms, such as the Bohr model.

2. any theory that treats certain phenomena by the methods of quantum mechanics.

   a quantum theory of gravitation.

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quantum theory British  

noun

1. 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 principle See wave mechanics

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quantum theory Scientific  

1. See quantum mechanics

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

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Etymology

Origin of quantum theory

First recorded in 1910–15

Example Sentences

See Examples For:

quantum theory

These understandings include attempts to reconcile general relativity with quantum theory — a challenge explored both in philosophy and popular science discussions.

From Science Daily ● Jun. 8, 2026

Unlike classical physics, which predicts precise trajectories for everyday objects such as cricket balls or communications satellites, quantum theory can only predict the likelihood of where a particle might be observed.

From Science Daily ● Mar. 10, 2026

Over time, Lorentz invariance became a foundational assumption in modern physics, especially within quantum theory.

From Science Daily ● Jan. 8, 2026

Despite their individual successes, quantum theory and general relativity do not fit together smoothly.

From Science Daily ● Jan. 8, 2026

Thus the radiation by black holes shows that quantum theory allows travel back in time on a microscopic scale and that such time travel can produce observable effects.

From "A Brief History of Time: And Other Essays" by Stephen Hawking