quantum

American  

[kwon-tuhm] / ˈkwɒn təm /

noun

plural

quanta

1. quantity or amount.

   the least quantum of evidence.

2. a particular amount.

3. a share or portion.

4. a large quantity; bulk.

5. Physics.

   1. the smallest quantity of radiant energy, equal to Planck's constant times the frequency of the associated radiation.

   2. the fundamental unit of a quantized physical magnitude, as angular momentum.

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adjective

1. sudden and significant.

   a quantum increase in productivity.

quantum British  

/ ˈkwɒntəm /

noun

1. physics

   1. the smallest quantity of some physical property, such as energy, that a system can possess according to the quantum theory

   2. a particle with such a unit of energy

2. amount or quantity, esp a specific amount

3. (often used with a negative) the least possible amount that can suffice

   there is not a quantum of evidence for your accusation

4. something that can be quantified or measured

5. (modifier) loosely, sudden, spectacular, or vitally important

   a quantum improvement

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quantum Scientific  

/ kwŏn′təm /

plural

quanta

1. A discrete, indivisible manifestation of a physical property, such as a force or angular momentum. Some quanta take the form of elementary particles; for example, the quantum of electromagnetic radiation is the photon, while the quanta of the weak force are the W and Z particles.

2. See also quantum state

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Etymology

Origin of quantum

1610–20; noun use of neuter of Latin quantus how much

Example Sentences

As these keys are already public, a quantum system wouldn’t be limited by the 10-minute window; it could use Shor’s algorithm to crack into these wallets at any time.

From Barron's • Apr. 1, 2026

Baskets of stocks tied to quantum computing, memes, expensive software names and autonomous driving all tallied big gains.

From MarketWatch • Apr. 1, 2026

One of the most promising approaches is quantum cryptography, which uses individual photons to generate encryption keys.

From Science Daily • Apr. 1, 2026

In the company’s view, a cryptographically relevant quantum computer could compromise most major blockchains by 2029.

From Barron's • Apr. 1, 2026

The disconcerting lessons of heliocentrism, of evolutionary theory, and of relativity and quantum theory are frequently cited cases in point.

From "Circumference" by Nicholas Nicastro