NISQ — Noisy Intermediate-Scale Quantum

A short, sharp explanation from Quantum London

Photo by Jayphen Simpson on Unsplash

NISQ stands for Noisy Intermediate-Scale Quantum. The phrase was coined by the quantum-legend-in-his-own-lifetime John Preskill in 2017.

Even with fault-tolerant quantum computing still a rather distant dream, we are now entering a pivotal new era in quantum technology. For this talk, I needed a name to describe this impending new era, so I made up a word: NISQ.

This stands for Noisy Intermediate-Scale Quantum.

Here “intermediate scale” refers to the size of quantum computers which will be available in the next few years, with a number of qubits ranging from 50 to a few hundred.

50 qubits is a significant milestone, because that’s beyond what can be simulated by brute force using the most powerful existing digital supercomputers. “Noisy” emphasizes that we’ll have imperfect control over those qubits; the noise will place serious limitations on what quantum devices can achieve in the near term.

We are currently in the NISQ era and while quantum hardware manufacturers are working to take us to a world with less-noisy, and thus more reliable, qubits much of the quantum software development and quantum algorithm design is focused on creating useful outcomes even with NISQ…