quantum mechanics

American  

noun

Physics.

1. a theory of the mechanics of atoms, molecules, and other physical systems that are subject to the uncertainty principle. QM

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quantum mechanics British  

noun

1. (functioning as singular) the branch of mechanics, based on the quantum theory used for interpreting the behaviour of elementary particles and atoms, which do not obey Newtonian mechanics

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quantum mechanics Scientific  

1. A fundamental theory of matter and energy that explains facts that previous physical theories were unable to account for, in particular the fact that energy is absorbed and released in small, discrete quantities (quanta), and that all matter displays both wavelike and particlelike properties, especially when viewed at atomic and subatomic scales. Quantum mechanics suggests that the behavior of matter and energy is inherently probabilistic and that the effect of the observer on the physical system being observed must be understood as a part of that system.

2. Also called quantum physics quantum theory

3. Compare classical physics See also probability wave quantum uncertainty principle wave-particle duality

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quantum mechanics Cultural  

1. The branch of physics that deals with the behavior of matter at the level of the atom, the nucleus, and the elementary particle. At this level, energy, mass, momentum, and other quantities do not vary continuously, as they do in the large-scale world, but come in discrete units, or quanta. (See Bohr atom and photon.)

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Other Word Forms

• quantum-mechanical
  adjective

Etymology

Origin of quantum mechanics

First recorded in 1920–25

Example Sentences

See Examples For:

quantum mechanics

The researchers also found that a version of the Schrödinger equation, the fundamental equation of quantum mechanics, can be expressed using entropic time.

From Science Daily ● Jul. 9, 2026

Whether quantum mechanics applies only to tiny particles or also to larger objects has been debated since the early days of the field.

From Science Daily ● Jul. 8, 2026

One of the most famous illustrations of quantum mechanics came in 1935, when Erwin Schrödinger proposed his cat paradox.

From Science Daily ● Jul. 5, 2026

If the idea proves correct, the black hole information paradox may not require a revision of quantum mechanics after all.

From Science Daily ● Jul. 5, 2026

This solves all the infinity problems of quantum mechanics.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife