Interview with Prof. Martin Kliesch: Quantum Computing A conversation about qubits, waves, the passion for the field of research, and potential future application possibilities.

A quantum computer is often described as a PC with a super-drive that can execute an unimaginable number of computing processes in parallel. Can you explain how it accomplishes this?

Actually, it only takes three ingredients to understand how a quantum computer works. You need qubits, quantum gates, and the ability to read out the computational processes at the end.

Could you explain that in more detail?

Traditionally, computations are performed using bits. A bit is a system that can exist in two different states, usually denoted by 0 and 1. That is the smallest unit of information. In quantum computing, we compute with qubits instead of bits. Here, the classical states 0 and 1 can be superimposed. Sometimes it is said that a qubit is simultaneously in both states. That's a bit imprecise. More accurately, it's like, for instance, a guitar string that can vibrate in multiple specific frequencies that simply overlap.

How does the hardware function in this case?

The Zuse Z3, the first classical computer constructed by Konrad Zuse in Berlin in 1938, was based on electrical relays. At that time, it was unforeseeable that we would eventually work with microchips. It's similar in quantum computing. We cannot yet say which platform will prevail. There are models that work with quantum-mechanical electrical currents, called "superconducting qubits." Additionally, there are ion trap computers where ions are trapped and manipulated with electromagnetic fields, and there are several other platforms.

At what temperature does a quantum computer operate?

Ion traps function in a vacuum and are often cooled with gaseous helium. But there are other approaches where quantum computers practically need to be cooled to near absolute zero, approximately -273 degrees Celsius. When I visit colleagues conducting experiments with ion traps, although I'm not allowed to touch anything as a theorist—since I'm not detailed in hardware—it's fascinating to witness the live development.

The hope is to accelerate digital transformation with quantum computing. What might that look like?

The expectation that quantum computers will solve all sorts of problems that conventional computers cannot must be clarified. Quantum computing can only provide a potential "quantum speed-up" for specific computations. Also, hardware development is still at a stage where quantum computing has no practical advantage over conventional computing. I anticipate the first real quantum calculations with significant practical application potential in quantum chemistry and materials research.

What personally excites you about your field of research?

Since my studies, I've been fascinated by the beauty of mathematics, often inspired by physical insights. That's how I encountered quantum information theory. It helps to heavily abstract physical concepts and reduce them to their most important properties. This field also forms the basis for quantum computing. What excites me the most is when, through elegant mathematics, one manages to solve complex and practically relevant problems.

And how do you plan to shape the professorship?

My existing research program is significantly expanded through collaboration with Fujitsu and colleagues in Hamburg. One goal is to find more application areas for quantum computing, to understand which types of computations are suitable for it. From this perspective, I hope to contribute the crucial theoretical research in the Hamburg area with my research group.

After studying physics, mathematics, and completing his doctorate, the native Berliner Martin Kliesch found it challenging to exchange his hometown for Düsseldorf. He taught theoretical physics as the head of the "Quantum Technology" junior research group at the local university. He greatly enjoys Hamburg as a father of two. He assumed the Foundation Professorship for Quantum-Inspired and Quantum Optimization in November 2022. In his leisure time, the passionate rock climber enjoys traveling to the Franconian Switzerland.

Further information

Read the entire interview in the current spectrum (in German).

Future Lecture at TU Hamburg on the topic of Quantum Computing on April 12, 2023. Professor Martin Kliesch will deliver his inaugural lecture simultaneously with the Future Lecture.