Introducing CQ: A C-like API for Quantum Accelerated HPC

TL;DR

This paper introduces CQ, a C-like API designed for integrating quantum computing into high-performance computing applications, with a reference implementation supporting simulation and potential future quantum hardware integration.

Contribution

It presents a new API specification and a reference implementation that enable incremental quantum computing integration into classical HPC codes.

Findings

Provides a C-like API compatible with classical HPC languages

Includes a reference simulator built on QuEST

Supports experimentation with analogue quantum computing

Abstract

In this paper we present CQ, a specification for a C-like API for quantum accelerated HPC, as well as CQ-SimBE, a reference implementation of CQ written in C99, and built on top of the statevector simulator QuEST. CQ focuses on enabling the incremental integration of quantum computing into classical HPC codes by supporting runtime offloading from languages such as C and Fortran. It provides a way of describing and offloading quantum computations which is compatible with strictly and strongly typed compiled languages, and gives the programmer fine-grained control over classical data movement. The CQ Simulated Backend (CQ-SimBE) provides both a way to demonstrate the usage and utility of CQ, and a space to experiment with new features such as support for analogue quantum computing. Both the CQ specification and CQ-SimBE are open-source, and available in public repositories.