NISQ, What Noisy Intermediate-Scale Quantum Means

NISQ stands for Noisy Intermediate-Scale Quantum, and it is the name for the era of quantum computing we are living in right now. A NISQ machine has enough qubits to be interesting, too many for a classical computer to easily imitate, but no error correction, so noise limits what it can reliably do. The term captures both the promise and the frustration of today’s hardware. This guide explains where the term came from and why the word noisy is the whole point. It covers what these machines are actually good for, the two structural problems that cap them, and why the field now treats NISQ as a stepping stone. Understanding it is the quickest way to close the gap between quantum computing headlines and reality. NISQ means noisy and uncorrected. The defining feature is the absence of error correction, so accumulated noise caps how deep a circuit can run. It is an era, not a machine type. The term describes a stage that spans every hardware platform, from superconducting to trapped ions. Intermediate scale is about size. Preskill’s paper points to roughly fifty to a few hundred qubits, too many for brute-force simulation but far too few for fault tolerance.…