In the future, quantum computers could solve complex problems where today’s computers fall short, for example in the development of new materials or supply-chain planning. To date, however, the systems have been prone to errors and their use is mainly limited to research labs. Moreover, software development standards are still lacking. In a joint research project led by the Fraunhofer Institute for Industrial Engineering (IAO), researchers from the Karlsruhe Institute of Technology (KIT) and the FZI Research Center for Information Technology are now developing a holistic reference architecture for quantum software – a world first. After all, even the most powerful computers are useless if suitable programs are missing.

The reference architecture resulting from the FullStaQD project will serve as a common blueprint for future applications to be used on various types of quantum hardware, establishing a uniform standard for the development of quantum software right from the outset.

Software for Computers that Don’t Exist Yet

The problem is that there are no common standards, neither for hardware, nor for software. “The software landscape for quantum computing is really fragmented. For this reason, many software solutions are closely tied to a particular type of hardware,” said Philipp Kunst, project manager from Fraunhofer IAO. With technology continuing to evolve, programs often need to be adapted as well. At the same time, there are constantly new technical approaches for quantum computers. “This impairs collaboration and makes it difficult to develop software in the long-term.”

“We want to avoid a repetition of 1960s software crisis,” said Professor Ina Schaefer from KIT’s Institute of Information Security and Dependability (KASTEL). While powerful computers were available at that time, mature software for their use was missing.

A “Power Outlet” for Quantum Computing

This is why Schaefer’s team is developing a reference architecture instead of dedicated software for a certain quantum computer. This blueprint describes the future interplay of various types of quantum computers and software solutions. Schaefer uses an everyday example to explain how this works: “Nobody knows today which devices will be connected to a power outlet in 20 years. Nevertheless, there are standards for power sockets and plugs. They don’t specify the device to be constructed, but only how the devices interact with the power supply.”

This principle also applies to the new reference architecture: “We don’t define a particular type of quantum hardware nor specific applications. Instead, we describe the the functions performed by the individual layers of a quantum software system and their communication,” said Schaefer. This way, the architecture remains open for future technological innovations. At the same time, it establishes a foundation for the joint development of larger software systems by multiple teams.

Independent Development of Applications and Hardware

The reference architecture breaks down quantum software into three layers: applications, system functions, and hardware. On the applications layer, programs for specific tasks will be created, for example, in logistics or materials research. The hardware layer comprises the quantum computer. Between them, there is the system layer, which links the two areas.

“This way, it is possible to refine applications and hardware independently from each other. Those who work on new applications don’t have to know the technical details of the hardware. On the other hand, existing programs can easily be adapted to enhancements of the hardware,” said Oliver Denninger, head of the FZI Software Engineering research division. At the same time, new hardware technologies can evolve without the need to redevelop all software programs.

“To ensure that quantum computing will be economically viable in the future, we must develop the software side on par with the hardware,” Kunst said. The researchers will develop the required software modules in the next project phase.

The FullStaQD Project: from Idea to Practice

The first version of the reference architecture, which has been presented in the meantime, marks the first milestone in the FullStaQD project. In the next step, the project partners will develop an open-source reference implementation. It will provide freely available components and be presented in the year to come. The reference architecture is available online : https://fullstaqd.github.io/architecture/latest/

Germany’s Federal Ministry of Research, Technology and Space (BMFTR) is funding the project with about EUR 15 million, KIT receives roughly EUR 700,000.

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