Special Session: Noisy Intermediate-Scale Quantum (NISQ) Computers -- How They Work, How They Fail, How to Test Them?

TL;DR

This paper critically examines the capabilities, limitations, and testing methods of NISQ-era quantum computers, discussing their achievements, challenges, and future prospects in the context of quantum advantage.

Contribution

It provides a comprehensive assessment of NISQ computers, analyzing their current state, potential algorithms, and the hurdles to achieving scalable, error-corrected quantum computing.

Findings

NISQ devices have demonstrated quantum supremacy.

Variational algorithms are promising for NISQ applications.

Significant challenges remain for error correction and scalability.

Abstract

First quantum computers very recently have demonstrated "quantum supremacy" or "quantum advantage": Executing a computation that would have been impossible on a classical machine. Today's quantum computers follow the NISQ paradigm: They exhibit error rates that are much higher than in conventional electronics and have insufficient quantum resources to support powerful error correction protocols. This raises questions which relevant computations are within the reach of NISQ architectures. Several "NISQ-era algorithms" are assumed to match the specifics of such computers; for instance, variational optimisers are based on intertwining relatively short quantum and classical computations, thus maximizing the chances of success. This paper will critically assess the promise and challenge of NISQ computing. What has this field achieved so far, what are we likely to achieve soon, where do we have to be skeptical and wait for the advent of larger-scale fully error-corrected architectures?