How do you program a computer that doesn't exist yet? In a new project, researchers at the Karlsruhe Institute of Technology (KIT) are looking into this question and developing software for quantum computers - even though no such computers are working yet and may not be for decades to come. But once the hardware is available, it needs to be usable without further delay; even the most powerful quantum computer will certainly be useless without suitable programs.
"We want to be ready when the big breakthrough comes," said Professor Ina Schaefer from KIT's Institute of Information Security and Dependability (KASTEL). Quantum computers are seen as having great potential for especially complex tasks in fields such as materials research and supply chain optimization, but so far they are little more than delicate laboratory experiments. Their lack of practical uses is their main weakness. Current systems at the major technology companies have less computing power than a pocket calculator, are too likely to fail, and often deliver unreliable results.
Why Software without Hardware Makes Sense
Developing software for quantum computers is worthwhile anyway. "We simulate quantum computers on conventional computers and test our programs on basic use cases," said Domenik Eichhorn, a computer scientist who also works at KASTEL. Eichhorn pointed to the so-called software crisis of the 1960s, noting that "Back then there were suddenly high-performance computers, but hardly any usable programs to run on them. We want to avoid that this time."
Programming Like in the Early Days of Computing
Special programming languages, for example Qiskit and Q#, are already available. "Like early computer languages, they're very hardware-based," Eichhorn said. That means the people programming them must know exactly how individual steps in the computing process work inside a quantum computer. Functionality typical of modern programming languages, such as automatic error correction or graphical user interfaces, is lacking thus far. "It's like the early days of classical computing in the 1950s," Eichhorn said. "Back then programmers still had to work with punch cards or very basic languages like assembly language that directly addressed the processors. It's like that today with quantum computers, except that the underlying technology is much more sophisticated."
What Makes Quantum Computers Special
Instead of bits, quantum computers work with qubits. Thanks to quantum mechanical effects like superposition and entanglement, qubits can assume multiple states simultaneously. In theory, this makes enormous computing power possible. The challenge, according to Eichhorn, is that "We have to develop algorithms that work with probabilities but still deliver reliable results."
KIT and Partners Collaborating on Quantum Software Research and Development
To prepare for the practical use of quantum computers in the future, the Quantum Software, Algorithms, and Systems priority program, which will be launched on September 1, and the QuSol project will pool research activities in industry and academia. In these initiatives, KIT researchers are focusing on developing application-oriented software to establish a foundation for future applications in fields such as logistics, materials research and cryptography. The German Research Foundation is funding the priority program, and Germany's Federal Ministry of Research, Technology and Space is funding QuSol.
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Being "The Research University in the Helmholtz Association", KIT creates and imparts knowledge for the society and the environment. It is the objective to make significant contributions to the global challenges in the fields of energy, mobility, and information. For this, about 10,000 employees cooperate in a broad range of disciplines in natural sciences, engineering sciences, economics, and the humanities and social sciences. KIT prepares its 22,800 students for responsible tasks in society, industry, and science by offering research-based study programs. Innovation efforts at KIT build a bridge between important scientific findings and their application for the benefit of society, economic prosperity, and the preservation of our natural basis of life. KIT is one of the German universities of excellence.
