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.

---

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

---

quantum theory Scientific  

1. See quantum mechanics

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

---

Etymology

Origin of quantum theory

First recorded in 1910–15

Example Sentences

See Examples For:

quantum theory

Interpretations mainly offer different conceptual explanations for what quantum theory means, while typically producing the same experimental predictions as standard quantum mechanics.

From Science Daily ● Sep. 11, 2026

"We can apply these generalized laws to better understand evaporating black holes in quantum theory and black hole mergers, like those detected by the LIGO-Virgo-KAGRA collaboration using gravitational waves."

From Science Daily ● Jul. 13, 2026

Physicists still lack a complete quantum theory of gravity that describes gravity at the smallest scales.

From Science Daily ● Jun. 19, 2026

As these possible paths overlapped later in the experiment, they produced a detectable striped interference pattern that matched the predictions of quantum theory.

From Science Daily ● May 11, 2026

One has to use a quantum theory of gravity to understand how the universe began.

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