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Within a few years, or at least in this decade, it should happen. The first working quantum computer will become a reality. When it does, it will be a breakthrough comparable to the arrival of the internet. A quantum computer can do calculations that today’s ordinary computers can only dream of. Big and small questions in fields such as chemistry, biology and medical science should then be much easier to solve. But before we get to that point, there is a lot of research left to be done.

One of the places where this research is being conducted is at Science Park, at the Faculty of Science. There, assistant professor Michael Walter works within the Korteweg-de Vries Institute for Mathematics (KdVI), the Institute of Physics (IoP) and the Institute for Logic, Language and Computation (ILLC). He is also a senior researcher at QuSoft, the research centre for quantum software. After studying mathematics and computer science in Germany, he obtained his doctorate in physics from ETH Zürich, with a thesis on quantum information.

That was in 2014. At the time, quantum information was already attracting a fair amount of attention. Today, in 2021, the whole world knows what quantum computers are and we eagerly await the arrival of these supercomputers. Walter’s field of research is booming.

‘This is a very exciting experience for all of us,’ says Walter. ‘I am very curious to see where quantum computers will take us. We already know that they can prove valuable in a wide range of applications. I feel like we are part of something bigger, something with which we can really make a difference. Through my research, I’m trying to find out which calculations these new computers can accelerate, and how. This means that I want to find new algorithms and gain insight into the complexity of quantum computations. I hope this knowledge can have an impact on our society.’

Michael Walter
Michael Walter

Quantum entanglement and optimisation

Walter’s research falls within quantum information theory, with some topics being more mathematical and others more physics-orientated in nature.

For example, he explores the phenomenon of quantum entanglement. Entanglement is when multiple quantum mechanical particles are ‘linked’ to one another, although they may be very far apart, and adopt each other’s properties. If one particle changes, in other words, the properties of the other particle(s) change with it.

Walter elaborates: ‘For me, entanglement is the common thread that unites all my research. It is responsible for the speed of quantum algorithms and the power of quantum networks. This motivates us to better understand its mathematical structure. But there are also indications that entanglement can help us understand how spacetime can emerge from quantum mechanics. These are all things I research with my students and colleagues.’

From the mathematical angle, he also explores another exciting area of research: quantum optimisation. In doing so, he aims to answer questions such as: how can quantum algorithms help speed up optimisation tasks in quantum computers? What is possible and what is not?

Walter says: ‘Optimisation is incredibly important. Think, for instance, of maximising throughput in a factory or optimising the distribution of vaccines. Many mathematical problems can be formulated in the language of optimisation. This offers a wealth of possibilities. Quantum algorithms can have a major impact in this area.’

Theory versus practice

What is unique about Walter’s research is not only that it moves between three different disciplines – mathematics, computer science and physics – but also that he is focusing on both fundamental and applied science. Walter recently received an Early Career Award from the Royal Netherlands Academy of Arts and Sciences (KNAW) for his interdisciplinary research.

‘At its core, my research is fundamental,’ he says. ‘But some of it is more applied. I’m happy to be doing both. The fundamental kind, supplemented by research that lets me touch the “real” world. I work on a variety of projects in which I frequently collaborate with other universities, institutes and companies, too. In terms of mathematics and computer science, for example, I collaborate closely with colleagues of Berlin and Princeton, while on the physics side, I have on-going collaborations with Berkeley and Caltech. All those projects are different but related.’

It’s no coincidence that Walter ended up at the Faculty of Science. In the field of quantum computer science, there is almost no better place to be in Europe than the Science Park. ‘Amsterdam is certainly one of the strongest places when it comes to quantum computer science – not only in Europe, but worldwide. There are many excellent colleagues to work with at the UvA. And with the CWI next door, you have even more people close by to exchange thoughts with and challenge your ideas.’


In addition to his research, Walter also devotes attention to future generations of quantum researchers. He teaches the introductory course in Information Theory for a number of Bachelor’s programmes and Quantum Information Theory for the Master’s programmes.

‘While preparing lessons can certainly be time-consuming, it is well worth it. Especially when you see the students become enthusiastic about the topic.’ At KdVI, he is working with colleagues to set up a new specialisation in Discrete Mathematics and Quantum Information.

Walter has also started working with an even younger batch of students: ‘We’ve developed an online course about quantum computing for secondary school students called “Quantum Quest”. I think it’s very important to reach this group and get them excited about this field. Simply put, we’ll be needing a lot of new people in the future.’

The online lessons are not easy. The students spend a month working on various quantum computing problems. They get to hear a few lectures as well. ‘The online course is extremely successful. It teaches secondary- school students to program for quantum computers. Precisely because it’s a bit more difficult – the course material is nearly at the Bachelor’s level – they feel challenged and find it interesting to do.’

Moving forward together

That new generation is vital. There is still quite a bit of work to be done to create a working quantum computer. Within the Netherlands, effective collaboration is a key facilitator. Walter elaborates: ‘Each university has its own strength, which we use to strengthen each other. The experimentalists are excited because they are well on their way to building a quantum computer. This, in turn, greatly motivates us theoreticians to find surprising new algorithms.’

Michael Walter is assistant professor of Mathematics and Theoretical Physics at the University of Amsterdam and senior researcher at QuSoft. He received a Diploma (2010) from the University of Göttingen and a PhD (2014) from ETH Zürich. Before joining QuSoft, he was a postdoctoral research fellow at Stanford University.

Annual review Faculty of Science 2020

This interview was also published in the annual review of the University of Amsterdam Faculty of Science. Read our annual review for news and background on teaching and research at the Faculty of Science in 2020, including interviews with lecturers, researchers and students, facts and figures on enrolment and staff news about organisation developments and our valorisation activities.