Meaning
A sudden, dramatic advance or change - a jump to a new level rather than a gradual improvement. The physicists' joke is that in its native field a quantum leap is the smallest change an electron can make, so the popular sense is, strictly, the exact reverse of the original. Enthusiastic register, beloved of product launches; scientifically literate readers hear the smallest-possible-joke, so use with a wink or not at all. Regional use: General English; physics origin, Danish parent phrase.
Origin
In quantum mechanics, the term names an electron's discontinuous jump between energy levels in an atom - an idea Niels Bohr first theorized in 1913, with the Franck-Hertz experiment soon confirming that atomic energy states are quantized; the jumps themselves were not observed until 1986, in trapped barium and mercury ions. Wiktionary suggests the English phrase may be a calque of the Danish kvantespring, Bohr's own language, and records the figurative senses: an abrupt, extreme change, and - flagged as nonstandard - the looser sense of a large, massive, significant change that advertising prefers. The irony is not lost on scientists; a 2010 New Scientist letter sniped that science would have to progress in quantum leaps, each with infinitesimal probability. Politicians are undeterred: a 1993 congressional hearing was already praising a quantum leap forward over the Mengistu government.
Research Sources
References used to check this entry’s meaning, history, or documented forms.
Variants
- a quantum leap forward
- quantum jump
- quantum leaps
Usage Examples
- Moving from paper ledgers to live dashboards was a quantum leap for the audit team, whatever the invoices say.
- The sequel is a quantum leap forward: the same engine, but nothing else survives from 2011.
- Purists wince when adverts promise quantum leaps, since the real thing is the smallest jump physics allows.