Endless possibilities

They say that quantum computers will revolutionise our lives. In a way, it all began at the Kiel Fjord: Max Planck, the Nobel Prize winner from Kiel, is considered to be the founder of quantum physics, and quantum materials are researched at the CAU today. The QuantumBay initiative now aims to boost the use of quantum computers in Kiel.

Symbol inage: Complex virtual cube in digital space
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In quantum computing, the bit, the smallest unit of information used by today's processors, becomes a quantum bit, or qubit for short. "Whereas a bit either has the state 0 or 1, a qubit can also have all possible combinations of the two. If a special kind of this superposition occurs with several qubits, the possibilities are endless," explained physicist Kai Rossnagel, to describe one of the unusual quantum mechanical effects with which the new, extremely powerful computers work. For example, this enables complex processes in materials to be calculated more precisely, large databases to be searched faster or absolutely secure encryption techniques to be developed.

From bit to qubit

The professor at the Institute of Experimental and Applied Physics (IEAP) is one of the spokespersons of the Kiel Nano, Surface and Interface Science (KiNSIS) priority research area and together with colleagues is also part of the QuantumBay initiative based in Kiel. "We cannot yet even estimate the full potential of quantum computers, as was initially the case with smartphones or the Internet. But the fact is: they will come," said Henning Rabe, one of the founders of the initiative. The business expert used to advise companies, but now, together with the network of science and industry, he wants to help advance the use of quantum computers. They could calculate complex dependencies from large volumes of data in medicine, climate or logistics at ultra-fast speeds, and for example predict climate developments more precisely.

The Federal Government has also recognised the potential and it has launched a funding programme for developing the new hardware and software required for quantum computers.

Although today's high-performance computers can already model highly complex relationships, their processing is sequential and it would take years for them to solve certain problems. Quantum computers sometimes only require a fraction of the time because they work in parallel and exploit quantum effects. "In order to make decisions, we need to understand phenomena in real time," emphasised Rabe. In order to use the quirky qubits for calculations, they are "calmed" and cooled down almost to the lowest possible temperature of minus 273.15 degrees Celsius. This requires a lot of space and is why quantum computers such as those already built by companies like IBM and Google are still very large. "The current state of technology is comparable to that of the 1940s, when a computer was still as big as an entire sports hall," said Rossnagel.

Making "sensitive" qubits more robust

There is another problem, in that qubits are highly sensitive – external influences can easily destroy their state and thus their calculations. Different concepts are currently being discussed regarding how powerful quantum computers might look. One approach is to use as many qubits as possible for mutual safeguarding. Rossnagel and some of his KiNSIS colleagues want to develop less sensitive qubits instead. They are researching quantum materials with unusual electronic properties. Complex interactions exist between the numerous electrons inside, which is why they behave completely differently to conventional materials. "We work with so-called topological materials and structures, which are very robust. Their electrons are closely connected and are not so easily separated," explained Rossnagel. Using state-of-the-art high-performance instruments such as those in the Ruprecht Haensel Laboratory (RHL), a joint facility of the CAU and the Deutsches Elektronen-Synchrotron (DESY) in Hamburg, the researchers look into the interior of such materials and investigate, for example, the ultra-fast movements of the electrons.

However, research not only drives the development of quantum computers, it also benefits from such tools itself. "With quantum computers, we could design complex materials with completely new properties – one reason why this field is so incredibly exciting," said Rossnagel. Will quantum computers also eventually replace our PCs at home, or are they just for laboratories and large companies? Rabe smiled. "Since we also couldn't imagine many other things in the past, I would never say never."

Author: Julia Siekmann

The QuantumBay initiative in Kiel

The goal of the QuantumBay initiative, launched privately in 2021, is a quantum computer centre at the Kiel Fjord focusing on application, ranging from the training and further education of programming specialists right through to the development of own solutions. Discussions are ongoing with interested partners from science, business and politics. Technical expertise in fields such as physics, computer science and life sciences is provided by members of the KiNSIS priority research area. jus


1. World Quantum Day

On 14 April 2022, the first World Quantum Day, researchers worldwide will celebrate quantum technologies with numerous events. Kai Rossnagel, professor at the CAU and DESY, is organising a public lecture on quantum physics at DESY together with partners from northern Germany. (jus)