The word "quantum" does not mean "very large," which is what I think you are trying to convey here. In this context it would mean "minimal" or "very small."
It absolutely can, and often does, mean "very large." Or, more precisely, "very significant, dramatic change."
A quantum jump, or quantum leap is, in physics, "an abrupt transition of an electron, atom, or molecule from one quantum state to another, with the absorption or emission of a quantum."
The emphasis is on abrupt transition ... sudden, dramatic change.
That doesn't necessarily mean "large," but in a non-physics, idiomatic, context it can certainly imply it. In spite of quantum mechanics being the world of the very small, the idiom really has nothing to do with the idea of "small."
p.s. KB, you were right about "quantum," but wrong about the phrase "quantum leap" or "quantum jump." Totally separate ideas, especially when applied idiomatically.