"We measure where no one has measured before"

What brought you to this field? Why does it fascinate you?

After leaving school, I thought a university degree would certainly be good to postpone the responsibilities in life a little longer (laughs). Since the social life was also important to me, I first mingled a bit with Germanists, medical doctors and historians and then started rather by chance with electrical engineering at ETH. After I had "survived" the exams rather badly in the first year, the "aha" experience came in the physics lecture in the second year. Suddenly I was hooked and never let go! I was particularly fascinated by the challenge of using light to resolve structures that are smaller than the wavelength of light. In other words, to depict things that no one has ever seen before.

What is the impact of your research on society?

On the one hand, we generate optoelectronic components with nanomaterials, e.g. light sources, photodetectors or modulators with the smallest dimensions. This brings advantages in terms of speed and efficiency. The goal is to bring photons – i.e. light – onto the computer chip and thus enable the optical processing of information.
On the other hand, we can use light to influence and control the degrees of freedom of matter. For example, the radiation pressure of light can set mechanical objects in motion, just as the sun does with satellites. In short, when we illuminate an object to measure it, we disturb it. If we can control this backaction, then we can push measurement accuracies to the fundamental limit.

What are currently the biggest challenges in your field of research?

Our continuous world loses its way the smaller we go: Currents become electrons, light becomes photons, matter becomes atoms, and thus the rules of the game change. We cannot scale down our electrical, optical and mechanical components any further and have to rethink. Quantum mechanics allows us to expand this scope, because the rules of the quantum world lead to new phenomena and states of matter. It allows us to have an electron, photon or atom in multiple places at once. Distant particles can be entangled with each other. We have not exploited this degree of freedom until now. If a particle is in two places at the same time, we have made two out of one and can use this. In my research, we are currently trying to do just that with levitating nanoparticles.

Another challenge here is how far we can take quantum mechanics into our macroscopic world. This chapter has not yet been written; how classical and quantum mechanics merge into each other, there are theories, but few experiments. This is what we now want to investigate: When will a classical object, e.g. a nanoparticle consisting of billions of atoms, behave quantum mechanically so that it exists in two places at the same time.

Since autumn 2019, the D-ITET has been offering a Master's programme in "Quantum Engineering" in collaboration with the Department of Physics. How did it come about?

If you think about how engineering has developed, you will notice that in the past there was simply the field of natural sciences. At some point, one realised that you could generate applications with mechanics. As a result, mechanical engineering split off from physics. Later, the same thing happened with electrical engineering, which emerged from electromagnetism. Now the time was ripe for another split: with quantum engineering as a new field, we are taking quantum mechanics and translating it into technologies, thus generating an independent field from it. The legitimacy for this is very high: there are already many products based on quantum technology: from NMR (nuclear magnetic resonance) to atomic clocks and lasers. Of course, it takes courage and a willingness to take risks every time to leave well-trodden paths and dare to do something completely new, but it is worth it. Our students have this pioneering spirit.

Quantum engineering covers areas such as sensor technology, information transfer and process simulation. Theoretically, it is also possible to build powerful quantum computers, which would make it easier to solve many mathematical problems, for example. The field of quantum engineering is broadly defined and generally refers to the development of technologies based on the laws of quantum mechanics.

How do you like ETH as a research institution?

ETH is excellent! Anyone who complains about this university can never have been anywhere else! However, when I came back to ETH in 2012 after 16 years in the US, I first had to adjust to the habits here. Switzerland likes precision and perfection. That's good, but it can limit the freedom for improvisation and creativity. We have to be careful that we don't block our scope for innovation and that regulations don't gain the upper hand. An over-regulated system does not make mistakes, but it does not create anything new either!

Are you collaborating with other people at D-ITET or other departments at ETH Zurich?

I collaborate with many groups, including Prof. Luisier, Prof. Leuthold, Prof. Benini, Prof. Wood etc. We also have collaborations with colleagues at D-PHYS and D-MAVT. Science today is a team sport, you have to work together and complement each other to make a difference. ETH is a very good place for this: the expertise is broad, the research groups are top.

How is your group composed? Are you looking for doctoral students?

We are quite international, with scientific staff from a dozen countries. In addition, my group, which comprises a good 20 people, is very interdisciplinary. About half have studied physics, the other engineering, and there are also people from the field of biomedicine. Now, in Corona times, everyone is very committed to the common good. That's great to see! We are always looking for motivated doctoral students, but not desperately.

What lectures are you giving this semester and next semester?

This semester I am only marginally involved. Namely, in the "Case Studies" in the aforementioned Master's in Quantum Engineering and in the "Nano-Optics" lecture, also at Master's level, which Dr. Martin Frimmer is reading this year. Next semester I will give the lecture "Electromagnetic Fields and Waves" for the second year of the Bachelor’s. In addition, I am currently developing a new lecture in the field of "Coupled Mode Theory", which creates an elegant transition from the classical to the quantum world.

Will the Corona crisis have a lasting effect on teaching and research?

Quite clearly, yes! The corona pandemic provides an opportunity for rethinking, we are compelled to be inventive and test alternative forms of learning and teaching. What works will be retained, e.g. digital professional conferences overseas, which I can now attend digitally even if I am only interested in a particular lecture. On the other hand, human contact in teaching, as in all other areas of life, will not be replaced in the long run. People are social beings who need direct exchange to get to know each other and build trust.

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