A quantum leap is a huge increase or a big move forward. You might describe the dramatic improvement in your math grade as a quantum leap.
An advance or sudden change is a quantum leap. You could say that schools in the United States have made a quantum leap in the availability of technology over the past ten years, or that a quantum leap in access to clean water is desperately needed in many developing countries. The phrase comes from a scientific term — in physics, a quantum leap is the abrupt change of a particle from one state to another. The Latin root, quantum, means "how much."