Productive Quantum Programming Needs Better Abstract Machines

TL;DR

This paper emphasizes the importance of a well-designed quantum abstract machine (QAM) for advancing quantum programming, proposing a framework to evaluate and guide the development of optimal QAMs for better software abstraction.

Contribution

It introduces a novel framework with criteria for evaluating QAMs, surveys existing proposals, and identifies gaps toward designing an ideal quantum abstract machine.

Findings

Existing QAM proposals share strengths but fall short of the ideal.

The framework helps compare and assess QAMs based on key criteria.

Guides future development of QAMs for better quantum software abstraction.

Abstract

An effective, accessible abstraction hierarchy has made using and programming computers possible for people across all disciplines. Establishing such a hierarchy for quantum programming is an outstanding challenge, especially due to a proliferation of different conventions and the rapid pace of innovation. One critical portion of the hierarchy is the abstract machine, the layer that separates a programmer's mental model of the hardware from its physical realization. Drawing on historical parallels in classical computing, we explain why having the "right" quantum abstract machine (QAM) is essential for making progress in the field and propose a novel framework for evaluating QAMs based on a set of desirable criteria. These criteria capture aspects of a QAM such as universality, compactness, expressiveness, and composability, which aid in the representation of quantum programs. By defining this framework we take steps toward defining an optimal QAM. We further apply our framework to survey the landscape of existing proposals, draw comparisons, and assess them based on our criteria. While these proposals share many common strengths, we find that each falls short of our ideal. Our framework and our findings set a direction for subsequent efforts to define a future QAM that is both straightforward to map to a variety of quantum computers, and provides a stable abstraction for quantum software development.