I know what the person using it means (that is, a lot of progress has been made), but I've learned that a quantum is the smallest amount of something that is possible. So, the phrase literally means the smallest leap (in progress) possible.
My questions are these: Is there more than one way of defining a quantum, and if not, why is quantum used to mean pretty much the antonym of what it actually does? Is it simply a case of people attempting to use scientific terms without knowing their meaning in an attempt to sound more intelligent?
Re: "Quantum Leap".
The term comes from physics and origiasnnly referred to the movement of an electron orbiting an atom. This entry from Wikipedia says it all.
Originally Posted by RobbieCook
This article is about the physical phenomenon. For the television program, see Quantum Leap. In physics, a quantum leap or quantum jump is a change of an electron within an atom from one energy state to the next. This is a discontinuous change in which the electron goes from one energy level to another without passing through any intermediate levels. This phenomenon contradicted expectations set by theories older than quantum mechanics that energy should always change continuously.
More generally, a quantum leap is the smallest possible change, as when one's bank account balance goes from $500.00 (five hundred dollars) to $500.01 (five hundred dollars and one cent). There are no possible amounts intermediate between those.
Vernacular, slang, or metaphorical usage
In the vernacular, the term quantum leap has come to mean an abrupt change, especially an advance or augmentation. The term dates back to early-to-mid-20th century.
It is sometimes said that a phrase such as 'a quantum leap in technology' is inappropriate, because 'quantum' supposedly means 'small' in quantum mechanics, so a 'quantum leap' would be a 'small advance'. However, 'quantum' does not actually mean 'small' in quantum mechanics; it means 'indivisible' or 'all-at-once'; but that indivisible logically implies smallest-possible. A quantum leap is an advance that happens all at once, rather than gradually over time. If advances are classified as either evolutionary or revolutionary, then a quantum leap would be the latter.
Re: "Quantum Leap".
It's a bit like 'meteoric rise' when meteors tend to fall.