The computer industry, with over seven decades of experience to draw on, has shown that to thrive, there must be a community of software engineers that produce the applications users depend on. Supporting those software engineers so they can write code that performs well across multiple generations of hardware (since application software generally lasts longer than hardware) is fundamental to sustaining the computer industry. Today's quantum software developers must reason at a low level, close to the hardware, which is not sustainable. In this paper, we assert that quantum computing needs high-level abstractions that support a quantum computing applications ecosystem. A single abstraction that bridges from the mental models used by a programmer to the details of how qubits are realized in hardware is unlikely to work. We need a hierarchy of tightly coupled models that define a framework for reasoning about the software development process in quantum computing. We propose an abstraction hierarchy and then explore its utility with two approaches to the eigenvalue estimation problem: (1) a variational algorithm with error mitigation, and (2) phase estimation with error correction. We use our proposed abstraction hierarchy to pinpoint key differences between these approaches and demonstrate how an abstraction hierarchy helps us understand software development. This supports our central conclusion; that it is not enough to understand individual components of a software stack. To make progress, we need to think about an abstraction hierarchy holistically.
The computer industry, with over seven decades of experience to draw on, has shown that to thrive, there must be a community of software engineers that produce the applications users depend on. Supporting those software engineers so they can write code that performs well across multiple generations of hardware (since application software generally lasts longer than hardware) is fundamental to sustaining the computer industry. Today's quantum software developers must reason at a low level, close to the hardware, which is not sustainable. In this paper, we assert that quantum computing needs high-level abstractions that support a quantum computing applications ecosystem. A single abstraction that bridges from the mental models used by a programmer to the details of how qubits are realized in hardware is unlikely to work. We need a hierarchy of tightly coupled models that define a framework for reasoning about the software development process in quantum computing. We propose an abstraction hierarchy and then explore its utility with two approaches to the eigenvalue estimation problem: (1) a variational algorithm with error mitigation, and (2) phase estimation with error correction. We use our proposed abstraction hierarchy to pinpoint key differences between these approaches and demonstrate how an abstraction hierarchy helps us understand software development. This supports our central conclusion; that it is not enough to understand individual components of a software stack. To make progress, we need to think about an abstraction hierarchy holistically.
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.
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.
Quantum computing is the latest revolution in computing and will probably come to be seen as an advance as important as the steam engine or the information society. In the last few decades, our understanding of quantum computers has expanded and multiple efforts have been made to create languages, libraries, tools, and environments to facilitate their programming. Nonetheless, quantum computers are complex systems at the bottom of a stack of layers that programmers need to understand. Hence, efforts towards creating quantum programming languages and computing environments that can abstract low-level technology details have become crucial steps to achieve a useful quantum computing technology. However, most of these environments still lack many of the features that would be desirable, such as those outlined in The Talavera Manifesto for Quantum Software Engineering and Programming. For advancing quantum computing, we will need to develop quantum software engineering techniques and tools to ensure the feasibility of this new type of quantum software. To contribute to this goal, this paper provides a review of the main quantum software components and platforms. We also propose a set of quality requirements for the development of quantum software platforms and the conduct of their quality assessment.
This position paper argues that the quantum circuit model is not a practical representation of quantum software for three reasons. First, the quantum circuit model is not suitable for semantical reasoning and better mathematical frameworks exist. Second, the abstraction level is too low for programming and too high for pulse-level machine code. Lastly, by ignoring the existence of a target quantum computer on which the quantum software could run, the transformation from software to quantum circuit model makes assumptions that result in inefficient machine code lower in the quantum computing stack. Thus, we conclude that new interfaces between quantum software, compiler, and quantum hardware need to be created such that the abstraction level is both suitable for the software and the hardware.
Quantum computing is advancing rapidly, with notable progress in both hardware and algorithm development. However, to make quantum computing truly accessible and usable across disciplines, a comprehensive, efficient and unified software stack is essential. Such a software stack must be flexible enough to support diverse hardware platforms and evolving algorithms, while enabling programming models for a wide range of users from quantum specialists to users without deep quantum expertise. Additionally, a software stack must support dynamic resource management for efficient system utilization as well as seamless integration with classical High-Performance Computing (HPC) environments. The latter is key, as quantum systems are increasingly envisioned as accelerators within hybrid workflows, supporting various levels of integration from loosely to tightly coupled. Despite numerous discussions, conceptual proposals, and initial efforts in recent years, few tangible implementations of such full-featured software stacks currently exist.
Quantum computing is no longer only a scientific interest but is rapidly becoming an industrially available technology that can potentially overcome the limits of classical computation. Over the last years, all major companies have provided frameworks and programming languages that allow developers to create their quantum applications. This shift has led to the definition of a new discipline called quantum software engineering, which is demanded to define novel methods for engineering large-scale quantum applications. While the research community is successfully embracing this call, we notice a lack of systematic investigations into the state of the practice of quantum programming. Understanding the challenges that quantum developers face is vital to precisely define the aims of quantum software engineering. Hence, in this paper, we first mine all the GitHub repositories that make use of the most used quantum programming frameworks currently on the market and then conduct coding analysis sessions to produce a taxonomy of the purposes for which quantum technologies are used. In the second place, we conduct a survey study that involves the contributors of the considered repositories, which aims to elicit the developers' opinions on the current adoption and challenges of quantum programming. On the one hand, the results highlight that the current adoption of quantum programming is still limited. On the other hand, there are many challenges that the software engineering community should carefully consider: these do not strictly pertain to technical concerns but also socio-technical matters.