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

Quantum batteries operate using core principles of quantum mechanics, including superposition and entanglement, rather than the chemical processes used in today's batteries.

From Science Daily • Apr. 4, 2026

"Similar to conventional batteries, quantum batteries charge, store and discharge energy. But while everyday batteries rely on chemical reactions, quantum batteries leverage properties of quantum mechanics," Associate Professor Hutchison said.

From Science Daily • Mar. 22, 2026

When the founders of quantum mechanics began exploring the strange behavior of matter and light, they realized Hamilton's framework was more than a simple analogy.

From Science Daily • Mar. 10, 2026

Meanwhile, quantum processors harness the properties of quantum mechanics, which makes them best suited for complex modeling tasks.

From Barron's • Jan. 29, 2026

Unfortunately for Einstein, the laws of quantum mechanics work incredibly well, and you can’t successfully explain quantum effects with traditional classical physics.

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