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NISQ (Noisy Intermediate-Scale Quantum)

Noisy Intermediate‑Scale Quantum (NISQ) describes a regime of quantum computers with fewer than 1,000 physical qubits, no scalable quantum error correction, and high susceptibility to environmental noise. NISQ devices can execute quantum circuits but are limited by decoherence, gate errors, and readout noise.

Origin

The term NISQ was coined by John Preskill in 2018 to characterize that era of quantum hardware.

Key Characteristics

  • Qubit count: typically < 1,000 physical qubits.
  • Error correction: lacks full, fault‑tolerant quantum error correction.
  • Noise sensitivity: operations are affected by decoherence, control errors, and measurement noise.
  • Practical implication: suitable for near‑term experiments and small‑scale algorithms but not for large, fault‑tolerant quantum programs.

    • Current Perspective

    As quantum error correction techniques and hardware improve, the field commonly treats the present period as a transitional phase between NISQ and fault‑tolerant quantum computing (FTQC). This framing reflects progress toward logical qubits and scalable error correction while acknowledging that many systems remain within the NISQ regime.

    Related Terms

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