The rapid development of quantum computing technology has opened new possibilities for solving complex problems beyond the capabilities of classical computing paradigms. However, combining quantum computing with classical systems to create Hybrid Quantum-Classical (HQC) software systems presents unique challenges that require novel approaches in software architecture. This paper proposes a foundation for developing Architecture Description Languages (ADLs) specifically for HQC systems. We aim to provide a robust framework for coherently describing, integrating, and analyzing quantum and classical computing elements. The paper discusses the design principles, methodology, and structural components of the architecture description languages and outlines future research directions.
The rapid development of quantum computing technology has opened new possibilities for solving complex problems beyond the capabilities of classical computing paradigms. However, combining quantum computing with classical systems to create Hybrid Quantum-Classical (HQC) software systems presents unique challenges that require novel approaches in software architecture. This paper proposes a foundation for developing Architecture Description Languages (ADLs) specifically for HQC systems. We aim to provide a robust framework for coherently describing, integrating, and analyzing quantum and classical computing elements. The paper discusses the design principles, methodology, and structural components of the architecture description languages and outlines future research directions.
Introduction: This article is the result of doctoral research conducted in 2025 on quantum software architecture, addressing the transformative potential of quantum computing and the challenges associated with integrating quantum capabilities into software systems. Problem: The lack of standardized architectural models for hybrid classical–quantum systems limits interoperability, reuse, and systematic software design. Objective: This study proposes a reference architecture to support the design and evolution of hybrid classical–quantum software systems. Methodology: The architecture was derived through a harmonization process. Results: The proposed framework defines ten architectural elements organized across three dimensions: Conceptual, Organizational, and Quality. Conclusion: The architecture provides a structured foundation for designing hybrid classical–quantum solutions. Originality: The work consolidates dispersed knowledge into a unified framework for hybrid classical–quantum systems. Limitations: The model is based on the currently limited body of literature and industrial experience, requiring future validation.
Quantum software engineering (QSE) has emerged as a discipline to address the challenges associated with developing software systems in the context of advancing quantum computing technology. This paper explores architectural design patterns specific to QSE. Building on previous work highlighting the need for high-level patterns, we analyze emerging architectural approaches in quantum computing. We identify key challenges unique to hybrid quantum-classical systems and propose a preliminary taxonomy of QSE architectural patterns. These patterns address recurring design problems in areas such as quantum resource management and classical-quantum integration. We describe several potential patterns and discuss their theoretical applications in hybrid software systems. This work aims to provide a foundation for further research into standardizing QSE architectural practices, with the goal of enhancing various quality characteristics of hybrid software (e.g., modularity or maintainability) in the NISQ era and beyond.
Quantum Software (QSW) uses the principles of quantum mechanics, specifically programming quantum bits (qubits) that manipulate quantum gates, to implement quantum computing systems. QSW has become a specialized field of software development, requiring specific notations, languages, patterns, and tools for mapping the behavior of qubits and the structure of quantum gates to components and connectors of QSW architectures. To support declarative modeling of QSW, we aim to enable architecture-driven development, where software engineers can design, program, and evaluate quantum software systems by abstracting complex details through high-level components and connectors. We introduce QADL (Quantum Architecture Description Language), which provides a specification language, design space, and execution environment for architecting QSW. Inspired by classical ADLs, QADL offers (1) a graphical interface to specify and design QSW components, (2) a parser for syntactical correctness, and (3) an execution environment by integrating QADL with IBM Qiskit. The initial evaluation of QADL is based on usability assessments by a team of quantum physicists and software engineers, using quantum algorithms such as Quantum Teleportation and Grover's Search. QADL offers a pioneering specification language and environment for QSW architecture. A demo is available at https://youtu.be/xaplHH_3NtQ.
As quantum computing continues to advance, the development of reliable and scalable quantum software systems becomes increasingly crucial. However, designing and implementing hybrid (quantum-classical) software systems poses unique challenges that require novel approaches and best practices. This position paper argues for the importance of developing architectural and design patterns specific to Quantum Software Engineering (QSE). We provide an overview of existing quantum software design patterns (more focused on low-level, programming details) and highlight the lack of patterns addressing hybrid software systems and architectural patterns. We discuss the key challenges that architectural patterns should address, including quantum-classical integration, maintainability, efficiency, and security. We also discuss the implications for practitioners, providing guidance on how to think high-level about hybrid software development process. Finally, we outline future research directions and emphasize the need for collaboration between the quantum computing and software engineering communities to establish a comprehensive high-level patterns framework for QSE.
Abstract Developers of the many promising quantum computing applications that currently exist are urging companies in many different sectors seriously consider integrating this new technology into their business. For these applications to function, not only are quantum computers required, but quantum software also. Accordingly, quantum software engineering has become an important research field, in that it attempts to apply or adapt existing methods and techniques (or propose new ones) for the analysis, design, coding, and testing of quantum software, as well as playing a key role in ensuring quality in large-scale productions. The design of quantum software nevertheless poses two main challenges: the modelling of software quantum elements must be done in high-level modelling languages; and the need to further develop so-called “hybrid information systems”, which combine quantum and classical software. To address these challenges, we first propose a quantum UML profile for analysing and designing hybrid information systems; we then demonstrate its applicability through various structural and behavioural diagrams such as use case, class, sequence, activity, and deployment. In comparison to certain other quantum domain-specific languages, this UML profile ensures compliance with a well-known international standard that is supported by many tools and is followed by an extensive community.
Addressing problems beyond classical computing limits is sparking an increasing interest in Quantum Computing. However, despite their adequacy to address specific problems, quantum algorithms cover a limited subset of the functionality required in real-world computing systems. Additionally, they require expensive specialized hardware. To overcome this issue, hybrid (quantum-classical) software systems are emerging as a promising way to integrate both computing paradigms by applying the principles of Service-Oriented Architectures (SOA). Still, the design and deployment of hybrid service-based systems faces unique challenges like the idiosyncrasies and constraints of NISQ computers (e.g., algorithms that can only run in specific machines, disparate quality attribute metrics), and the management of structural and behavioural properties of service-based applications. From the SOA perspective, architectural decisions need to be made by performing a trade-off analysis and providing quantitative guarantees of system configurations under prescribed levels of uncertainty. In this paper, a method to explore the design space of quantum-classical applications is provided by a formalization of an architectural style of hybrid applications. The obtained results demonstrate that the proposed method successfully identifies decision boundaries. It enables the dynamic selection of the most suitable hybrid or classical configuration based on the user's QoS criteria.