# quantum

Pronunciation: say "KWON-tuhm" US /ˈkwɑntəm/, UK /ˈkwɒntəm/

## Adjective

1. Relating to quanta, quantum mechanics, or technologies based on quantum physics, including quantum computers.
   - Simple: Related to quantum physics or technologies that use it, such as quantum computers.
   - _Quantum effects such as tunneling let particles slip through barriers they could not cross in classical physics._
   - _For decades, physicists have tried to reconcile gravity with quantum theory._
2. Of a change or advance, sudden and very large or significant, rather than gradual. *(colloquial)*
   - Simple: Describes a change that is very big and important, often happening all at once instead of slowly.
   - _The new engine represents a quantum leap in fuel efficiency._
   - _Remote work has brought a quantum shift in how companies think about office space._

## Noun

3. The smallest possible unit of a given quantity or measurable phenomenon, which for that reason cannot be divided.
   - Simple: The smallest amount of something, like energy or light, that cannot be split into smaller parts.
   - _An electron moves between energy levels by absorbing or emitting a single quantum._
   - _Light is absorbed and emitted only in whole quanta, never in fractions of one._
4. Short for quantum computing: the field of building and using computers that run on quantum physics. — Ellipsis of quantum computing.
   - Simple: Short for quantum computing. Used in tech talk about computers that run on quantum physics.
   - _Investors are pouring money into quantum, hoping for a breakthrough within the decade._
   - _The startup hires physicists and software engineers who want a career in quantum._
5. The amount or extent of something, especially in law, the amount of damages awarded or the severity of a sentence.
   - Simple: An amount of something, especially how much money a court awards or how heavy a punishment is.
   - _The ministry approved the fare hike, but the quantum of the increase is still being debated._
   - _Auditors are still working out the quantum of funds diverted from the project._

## Other meanings

- (noun) The amount of time allotted to a thread to do its work in a multithreaded system.
- (noun) In models of airborne infection, a unit dose of infectious particles that gives a susceptible person about a 63 percent chance of infection.
- (noun) A definite portion of a manifoldness, set off by a mark or enclosed by a boundary.

## Origin

Latin quantus ("how much") had a neuter form, and Late Latin used it as a noun, quantum.

Source: DictionaryAI, https://dictionaryai.com/define/quantum (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).