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

Macroscopicity allows scientists to evaluate experiments involving systems such as nano-oscillators, atomic interferometers, and nanoacoustic resonators by measuring how effectively they rule out even tiny deviations from standard quantum theory.

From Science Daily ● May 11, 2026

The research, published in Physical Review Research, also offers a possible way to test these models against standard quantum theory.

From Science Daily ● May 3, 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

For the moment, however, we shall turn to the recent attempts to bring together our understanding of the other forces of nature into a single, unified quantum theory.

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