What is quantum leap compared to change?

Change can happen over time,
a quantum leap does not.

The expression: a quantum leap comes from physics and refers to the orbit of electrons around the nucleus. The electrons cannot be anywhere but have to be in distinct energy regions. So for an electron to change orbit it must leap to the next energy or lower energy level it can not do it gradually.

Similarly if a quantum leap is made it is a radical change not a gradual change. New discoveries in science can revolutionise traditional thinking overnight. One could say a quantum leap in understanding was made. Whereas, just about everything can change slowly over time but that is not a quantum leap.

Change can be slow and gradual or even fast and high paced. The student quickly improved his language skills at the immersion school. Is an example of change.

A quantum leap is jumping from one understanding to another. The student finally understood the difference in verb endings for the past tense and a quantum leap was made in his ability to understand and speak intelligibly. Vast progress was made when an impediment (obstacle) was removed.