In December 2020, I published an article on the great utility of the QuantumPath® platform in the emerging quantum software business [1], based on its capabilities at the time of launch for software lifecycle management and agnostic and hybrid software development. After five years, I think it’s reasonable to summarise the advances made to the platform and update the features of QPath® for developing and integrating hybrid quantum/classical software systems.

When we first started developing quantum software in 2017–18, we realised that, to be useful, quantum software would have to be hybrid to integrate with classical software. Therefore, we set ourselves the challenge of creating professional technologies and tools that would facilitate the professional development of dynamically integrated hybrid software [2], capable of harmoniously integrating classical and quantum solutions, data, systems, etc. All this is achieved while complying with the basic principles of commercial quantum software: extensibility, security and high quality [3].

A few years later, we felt that this challenge was reinforced when both the “Talavera Manifesto for Software Engineering and Quantum Programming” [4] and the “National Agenda for Software Engineering Research and Development” [5] of the Software Engineering Institute at Carnegie Mellon University recognized the relevance of classical and quantum computing coexisting, and declared the importance of developing tools for continuously integrating quantum computers and hybridising quantum software systems with classical IT from a software engineering perspective.

As is well known, classical and quantum software are two very different computing paradigms, each designed to solve specific problems using different approaches. These two paradigms are complementary rather than mutually exclusive, and when combined properly, they will significantly enhance our capacity to process and use information.

Given the immense investment in classical software for general tasks that continues to be efficient and useful for owners and users, it is reasonable to conclude that hybridisation will be a significant part of the new software business. However, to participate successfully in this market, software solutions specially designed to facilitate the novel and complex integration of these two software worlds will be necessary.

Even before the current context emerged, classical computer science had already addressed and resolved various problems posed by traditional, complex software architectures for the dynamic integration of heterogeneous systems. Service Oriented Architecture (SOA) was defined as a software design paradigm that structures applications as autonomous, reusable, and modular services that can be used with guarantees over a network. This concept was consolidated in the 1990s by the growing need for reliable and secure distributed software systems, which were in high demand due to the increasing popularity of the internet. SOA facilitated integration and provided the scalability and flexibility demanded by industry, enabling independent systems to interact harmoniously thanks to the key characteristics of its services:

·       Autonomy

·       Independence from each other (weak or flexible coupling)

·       Interoperability (they do not depend on the environments and languages used in different applications)

·       Reusability

Drawing on years of experience in designing, developing and implementing successful classic software solutions based on SOA architecture, in 2018 the creators of QPath® embarked on a project to conceive, design and create specialised methods and tools to extend this service architecture to the quantum realm.

The result of this work was qSOA®, a high-level service architecture that is fully oriented towards business requirements and is specially designed to integrate quantum software with classical IT. It does this through open, robust and transparent protocols that simplify the development of industry-ready quantum/classical applications.