From "Pen and Paper" to automated solutions

Compilers are an important building block in this so-called "software stack". Applications today are written using "high-level languages" such as JavaScript, C++ or Python – programming languages that can be used to express highly complex functionalities. The programmer's code, called source code, is then translated into a language that the processor understands, and ultimately implemented with logic gates. This "translation" from programming language to machine language, known as compilation, runs completely automatically. In quantum computing, on the other hand, much of this is still done "with pen and paper," says Lukas. "We're at such an early stage that applications are largely programmed in such a way that people actually indicate sequences of individual quantum gates to be executed. Of course, that's not at all feasible or scalable in the long run," he explains. With today's computers, where there are billions of transistors on a chip, that would also be unthinkable. Developing automated solutions and ultimately ensuring that users can use quantum computers without having to be quantum or IT experts – "that's our mission for the probably longer-term future."

But it is precisely the fact that there is still so much to do on the part of computer science that drives Lukas: "I find the perspective of software development for novel systems, such as quantum computing, extremely exciting. You are at the forefront of science and can make big contributions in a relatively short time."

Initially, it was not at all clear to the young computer scientist that he wanted to go into research. After completing his master's degree in mathematics and while still writing his bachelor's thesis in computer science, he was already working for a company. But when Robert Wille offered him a position as a doctoral student, the decision was made quickly and the job was quit. When his doctoral supervisor moved to TUM during his Ph.D., it was clear to Lukas that he would go along – even if he wouldn't turn his back on his Austrian hometown to do so. Lukas still sees Linz as the center of his life: his girlfriend, a large group of friends from his childhood, the city where he feels at home. He will therefore often commute between Munich and Linz.

"In Munich, there are lots of people in the vicinity who are doing research on quantum computing and with whom you can exchange ideas."

Lukas sees the fact that his research group is now based in Munich as a great opportunity: "In Linz, we were one of the few groups working on quantum computing. In Munich, there are lots of people in the vicinity who are doing research on quantum computing and with whom you can exchange ideas." But this exchange also demands a lot from the scientists. "When we as computer scientists talk to physicists, it takes a lot of time to make sure that both parties mean the same thing," says the 29-year-old, thinking back to meetings with several MQV scientists that focused on compilation. Everyone speaks a different language, but if you don't talk to each other, you run the risk of solving the wrong problems, Lukas warns. Because a compiler acts as a translator from programming language to machine language, it makes a difference whether the processor uses superconducting qubits or qubits encoded in atoms. For example, when compiling programs, one has to be careful that, depending on the hardware technology, only certain quantum gates are supported or that not all qubits can "talk" to each other, the young computer scientist explains. "In order to write a compiler that compiles to a particular hardware in the best possible way, we need characteristics of the physical systems that we can put into our models." You have to try to understand the physics a little more, he says, while the physicists have to create levels of abstraction and not throw around physical details. "We have to somehow come together on this, because isolated solutions will not lead to success."

At noon, Lukas meets with Nils, Aaron and other doctoral students from the group. With his hands in the pockets of his shorts, he walks with his teammates from the TUM campus on Arcisstrasse over to the cafeteria. Since a bet in his school days, he always wears shorts, even in winter, unless there is a formal occasion that prevents him from doing so. It's almost like a trademark, Lukas says with a laugh. Perhaps also a sign of his optimistic streak. The sun will certainly shine warmly enough on this otherwise still chilly spring day.