quantum leap

A sudden or important change or improvement. Gary's new job in upper management is a quantum leap forward from his old position at the factory.

A dramatic advance, especially in knowledge or method, as in Establishing a central bank represents a quantum leap in this small country's development. This term originated as quantum jump in the mid-1900s in physics, where it denotes a sudden change from one energy state to another within an atom. Within a decade it was transferred to other advances, not necessarily sudden but very important ones.