No wonder quantum computing has become the subject of such hype. Machines that harness the weirdness of quantum mechanics are so alien — and promise such massive theoretical leaps in performance — that it is easy to believe nothing will be the same again.

Full-scale quantum machines are probably many years away. But in the meantime, a “good enough” form of the technology — not revolutionary but promising significant advances for some applications — is on the horizon. The world will not change overnight, but development timetables already show practical quantum machines arriving much sooner than seemed likely only a short time ago.

Computers made up of quantum bits (or qubits) that can be in two states at once, or “entangled” to act in unison, could enable computers that are a million times or more faster than current machines. On a large enough scale, they may crack the world’s hardest problems.