Quantum

A discrete amount of a physical quantity, especially energy, exchanged or possessed at the smallest scale relevant to a system. In quantum physics, allowed values often occur in discrete steps rather than continuously.

Connect

Planck constant: A fundamental constant that sets the scale of quantum effects and relates a photon’s energy to its frequency. It sets the scale of energy quanta through the relation between energy and frequency.
Quantum harmonic oscillator: A quantum system with a restoring force proportional to displacement and equally spaced energy levels. Its evenly spaced energy spectrum is a canonical model of quantized energy.
Black-body radiation: Electromagnetic radiation emitted by an ideal absorber whose spectrum depends only on its temperature. Its spectrum prompted Planck’s proposal that energy exchange occurs in discrete amounts.
Laser: A device that amplifies light through stimulated emission, producing a coherent beam. Laser operation depends on controlled transitions between quantized atomic or molecular energy levels.
Photon: The quantum of the electromagnetic field, carrying energy and momentum. A photon is a concrete example of a quantum exchanged by a physical field.
Quantum field theory: A framework describing particles as excitations of fields governed by quantum mechanics and special relativity. It treats particles as discrete field excitations, extending the quantum idea beyond bound systems.
Max Planck: German physicist who introduced energy quantization in 1900 to derive the black-body radiation spectrum. Planck introduced the original energy-element hypothesis that gave quantum its name.
Atomic clock: A clock that measures time using the frequency of a transition between atomic energy states. Its precision comes from stable frequencies associated with discrete quantum transitions.
Energy level: A permitted energy value of an atom, molecule, or other bound quantum system. Discrete energy levels make the idea of distinct energy amounts measurable in bound systems.
Absorption (electromagnetic radiation): The transfer of electromagnetic energy to matter when radiation is absorbed. Matter can absorb radiation in discrete photon-sized transfers matching its allowed transitions.