quantum
n pl , -ta
a the smallest quantity of some physical property, such as energy, that a system can possess according to the quantum theory
b 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 (C17: from Latin quantus (adj) how much)
quantum chromodynamics
n (Physics) a theory describing the strong interaction in terms of quarks and gluons, with the colour of quarks used as an analogue of charge and the gluon as an analogue of the photon, (Abbrev.)
QCD
(C20: chromodynamics from chromo- (referring to quark colour) + dynamics, modelled on quantum electrodynamics)
quantum efficiency
n
1 (Physics) the number of electrons released by a photocell per photon of incident radiation of a given energy
2 (Chem) the number of chemical species that undergo reaction per photon of absorbed radiation of a given energy
quantum electrodynamics
n (Physics) a relativistic quantum mechanical theory concerned with electromagnetic interactions, (Abbrev.)
QED
quantum electronics
n the application of quantum mechanics to the study of the generation and amplification of power at microwave frequencies in solid crystals
quantum field theory
n (Physics) quantum mechanical theory concerned with elementary particles, which are represented by fields whose normal modes of oscillation are quantized
quantum flavourdynamics
n a gauge theory of the electromagnetic and weak interactions, (Also called)
electroweak theory (Abbrev.)
QFD
(C20: flavourdynamics from flavour (referring to quark flavour) + dynamics, modelled on quantum electrodynamics)
quantum gravity
n (Physics) a theory of the gravitational interaction that involves quantum mechanics to explain the force
quantum leap , jump
n a sudden highly significant advance; breakthrough
(C20: from its use in physics meaning the sudden jump of an electron, atom, etc. from one energy level to another)
quantum mechanics
n functioning as sing 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 meruit (Latin) as much as he has earned: denoting a payment for goods or services in partial fulfilment of a contract or for those supplied when no price has been agreed
quantum number
n (Physics) one of a set of integers or half-integers characterizing the energy states of a particle or system of particles. A function of the number multiplied by a fixed quantity gives the amount of some specified physical quantity possessed by the system
quantum state
n (Physics) a state of a system characterized by a set of quantum numbers and represented by an eigenfunction. Each state has energy which has a value that is precise within the limits imposed by the uncertainty principle but which may be changed by applying a field of force. States that have the same energy are called degenerate
See also →
energy level
quantum statistics
n functioning as sing (Physics) statistics concerned with the distribution of a number of identical elementary particles, atoms, ions, or molecules among possible quantum states
quantum theory
n a theory concerning the behaviour of physical systems based on Planck's idea that they can only possess certain properties, such as energy and angular momentum, in discrete amounts (quanta). The theory later developed in several equivalent mathematical forms based on De Broglie's theory (see wave mechanics) and on the Heisenberg uncertainty principle