quantum leap
A sudden large advance, versus the physics sense.
In ordinary use, quantum leap means a sudden large advance. In physics a quantum jump is a discrete change of state, not a large one. The popular sense is established. In scientific writing, do not use the popular sense.
Examples
Use The new route was a quantum leap in time saved.
Use a discrete change of state
Avoid a quantum leap in the lab notes (If you mean only a large gain.)