NISQ Era

NISQ Era (Noisy Intermediate-Scale Quantum) describes the current period of quantum computing, characterized by devices with 50–1000 qubits that are too noisy for full quantum error correction but large enough to test variational and sampling algorithms. The term was coined by John Preskill in 2018 and has become the dominant framing for near-term quantum computing research.

The NISQ era is defined by a hardware gap: current devices have too few qubits to implement error correction codes with sufficient code distance, and their error rates are too high to run the algorithms (Shor's, Grover's, quantum simulation) that have proven quantum speedups. The variational algorithms (VQE, QAOA) that dominate the NISQ literature are hybrid classical-quantum approaches with unproven speedups. The Barren Plateau Problem suggests that these algorithms may be structurally flawed, not merely underpowered.

The critical systems question is whether the NISQ era is a necessary transitional phase or a costly detour. If fault-tolerant quantum computing requires a million qubits and NISQ devices have a thousand, the gap is not bridgeable by incremental improvement. The NISQ era may be a decade-long period where quantum devices are scientifically interesting but practically useless — a kind of quantum winter disguised as progress.