Three Questions for Prof. Dr. Otfried Gühne
In this three-question interview, we speak with Prof. Dr. Otfried Gühne, Professor at the University of Siegen. His research focuses on the theory of multiparticle entanglement and the foundations of quantum mechanics.
In his work, Prof. Gühne explores how complex quantum correlations arise, how they can be characterized and detected, and what they reveal about the fundamental principles governing quantum systems. In this short interview, he shares insights into his research perspective, key challenges in the field, and what motivates his work at the interface of theory and fundamental physics.
What is the focus of your research in the field of photonics and what originally attracted you to this field of study?
First, I'm a theorist, I'm not an experimentalist. I started with theory and then got more in contact with people doing photonic experiments. As a theorist, you always have abstract ideas about states and so on, but the experimentalists can prepare them and prove the entanglement. This is essentially how I got into contact with photonics groups a long time ago when I was a PhD student. It was very nice that, as a theorist, you do something or calculate something and then there are experimentalists who measure it. This was my very first contact with the photonics field!
Since then, I'm regularly collaborating with photonics groups from different places on topics such as how to see quantum effects in experiments, predicting things of entanglement, notions of entanglement, or preparing interesting quantum states.
What are some of the most surprising or unexpected applications of photonics that you have encountered in your research or studies?
It's already an interesting application if you see an interesting quantum effect. There are different levels of application. For instance, with photons you can do a lot of experiments concerning high dimensional entanglement, where you really use all the degrees of freedom of a photon. That means that you can encode high dimensional information, or you can use high dimensional quantum space, high dimensional Hilbert space. This is what’s surprising: it's sometimes surprising how far you can go! What I mean is that, traditionally, a single photon is described using simple degrees of freedom such as polarization, so it is either horizontal or vertical. But nowadays, experiments go far beyond this with additional degrees of freedom, such as orbital angular momentum or past degrees of freedom, allowing them to prepare highly entangled quantum states using only a single photon and to explore a wide range of new experimental possibilities.
And concerning real applications, for instance with quantum metrology, you can really use quantum effects to measure some fields more precisely. They do it for example with gravitational wave detectors. This is very promising, and somehow surprising.
What excites you most about the future of photonics, and where do you see your research taking you in the coming years?
The field of metrology and interferometry, I think this will become increasingly important. People are now using these interferometers for gravitational wave detection, which is very nice, but there will probably be other applications. For instance, people are now thinking of how to test quantum gravity in experiments, and this, I would say, is still far away. But for the future such experiments can be very promising.
The field of metrology and interferometry, I think this will become increasingly important. People are now using these interferometers for gravitational wave detection, which is very nice, but there will probably be other applications. For instance, people are now thinking of how to test quantum gravity in experiments, and this, I would say, is still far away. But for the future such experiments can be very promising.
Concerning my research, I would say in the coming years it's a lot about exploring properties of multi-particle states, meaning for instance multi-photon states, because from the theoretical side there are a lot of interesting effects in multi-particle entanglements that you cannot see if you have only two particles. There are a lot of interesting quantum states, which you can characterize with a lot of usefulness somehow, and this will be one of our fields in the next years. And of course, again, it would be very nice to see this in photonic experiments as well. I mean I'm only doing the theory, but let's hope!
