Since when did quantum mean tiny????
The phrase "quantum leap" does mean and has always meant a change in levels. Not an insignificant thing.
I originally learned the word in 1971 in Freshman High School Science Class in reference to energy states of electrons.
An orbiting electron in an atom makes jumps between energy levels, known as quantum leaps or jumps. The atom creates a photon when an electron moves to a lower energy level and absorbs a photon when an electron moves to a higher energy level or leaves the atom (ionization).
Which is, again, not an insignificant change in energy state. And explains how a luminous/phosphorescent watch display works.
As the word is defined fifty some years later:
1: discrete quantity of energy proportional in magnitude to the frequency of the radiation it represents.
2: an analogous discrete amount of any other physical quantity, such as momentum or electric charge.
3: the unit quantity of acetylcholine released at a neuromuscular junction by a single synaptic vesicle, contributing a discrete small voltage to the measured end-plate potential.
4: required or allowed amount, especially an amount of money legally payable in damages.
"the court must determine the quantum of compensation due"