What is a quantum simulator?

TL;DR

This paper clarifies the fundamental concepts of quantum simulators, distinguishing between simulation and computation, and explores the boundary between quantum and classical simulation methods, providing a comprehensive perspective on the field.

Contribution

It offers a detailed analysis of the nature, purpose, and accuracy of quantum simulators, and discusses the quantum-classical threshold in simulation techniques.

Findings

Distinction between simulation and computation clarified

Criteria for quantum versus classical simulation established

Overview of current achievements and future directions provided

Abstract

Quantum simulators are devices that actively use quantum effects to answer questions about model systems and, through them, real systems. Here we expand on this definition by answering several fundamental questions about the nature and use of quantum simulators. Our answers address two important areas. First, the difference between an operation termed simulation and another termed computation. This distinction is related to the purpose of an operation, as well as our confidence in and expectation of its accuracy. Second, the threshold between quantum and classical simulations. Throughout, we provide a perspective on the achievements and directions of the field of quantum simulation.