quantum mechanics

noun

, Physics.

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

quantum mechanics

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

quantum mechanics

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 physicsSee also probability wave

quantum mechanics

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 .)

Other Words From

• quantum-me·chani·cal adjective

Word History and Origins

Origin of quantum mechanics¹

First recorded in 1920–25

Example Sentences

These are our era’s version of the paradoxes of atoms and light that drove Einstein and others to develop quantum mechanics and relativity theory.

From Nautilus

He majored in mathematical physics, studying mind-bending theories of quantum mechanics and partial differential equations.

From The Daily Beast

Each type of atom and molecule has its own unique spectrum, according to the rules of quantum mechanics.

From The Daily Beast

He went off into a happy mist of quantum mechanics, oscillation theory, and periodic functions of a complex variable.

From Project Gutenberg

The man had used a simplified quantum mechanics without correction for relativistic effects.

From Project Gutenberg