The much-heralded arrival of quantum (0) SUPREMACY (SUPREME) — the point at which a quantum processor outperforms the most powerful classical machine on a chosen benchmark — has been announced, retracted and announced again with wearying frequency. What remains genuinely uncertain is the 1SCALE of current architectures: a device of fifty useful qubits is one thing, a device of fifty thousand quite another. Sustaining 2COHERE across such a system for long enough to perform meaningful 3COMPUTE is the central engineering challenge, and no credible roadmap yet eliminates it entirely. If the obstacle is overcome, conventional 4ENCRYPT protocols may rapidly face 5OBSOLETE, a prospect that has already spurred intensive research into post-quantum cryptography. The field's promise extends well beyond codebreaking; 6PROBABLE modelling of complex chemistry could transform drug discovery and materials science. Even so, seasoned physicists continue to speak about near-term commercial 7VIABLE rather 8SCEPTIC, warning that the gap between laboratory milestone and useful machine remains vast.