Prof. Jérôme Faist
Institute of Quantum Electronics, ETH Zürich
ABOUT THE SPEAKER
THE INTERVIEW
Jérôme Faist is a Swiss physicist and professor at the Institute of Quantum Electronics at ETH Zürich. He obtained his Bachelor’s degree in 1985 at EPF Lausanne. His Ph.D. studies focused on optoelectronics, in particular vertical-cavity surface-emitting lasers and optical modulators (doctoral degree in 1989). Following his doctorate, he worked at IBM in Rüschlikon as a post-doc between 1989 and 1991. In 1991, he switched to Federico Capasso’s group at Bell Laboratories, Lucent Technologies, in Murray Hill, New Jersey, where he first worked as a post-doc investigating intersubband transitions. In 1994, he succeeded in building an experimental quantum cascade laser using molecular-beam epitaxy, in collaboration with Federico Capasso, Deborah Sivco, Carlo Sirtori, Albert Hutchinson and Alfred Y. Cho.
In 1997, Faist became full professor at the University of Neuchâtel, Switzerland, where he remained until 2007. His work there focused mainly on mid- and far-infrared intersubband lasers. In 1998, he founded the spin-off company Alpes Lasers with the goal of commercialising the quantum cascade laser for scientific, industrial and medical use. In 2007, he became professor at the Institute of Quantum Electronics at ETH Zürich, and he also became head of the FIRST-lab Center for Micro- and Nanoscience at ETH.
His current research interests are the development of high-performance quantum cascade lasers in the mid- and far-infrared and the physics of coherence in intersubband transitions in the presence of strong magnetic fields.
Prof. Faist was invited to open the session dedicated to Laser Physics and Materials Science at the Open Readings 69th International Conference for Students of Physical and Natural Sciences by delivering a talk titled “Semiconductor quantum walk combs from the near-infrared to the terahertz”. After the lecture, the professor kindly agreed to give an interview about his current scientific work and academic achievements. He was interviewed by Assoc. Prof. Dr. Renata Butkutė, Deputy Head of the Optoelectronics Department at Center for Physical Sciences and Technology.
Probably the two main factors that had the most influence on my choice of profession were my physics teacher and my father. When I was still a schoolboy, I had a very good physics teacher, who interested me in simple physics laws by explaining them with examples from nature and everyday life. My father was a good electronics specialist and also instilled in me curiosity and an interest in what surrounds us and how it works. I realised quite early on that I liked both of these things and could successfully combine them — deep thinking and engineering professionalism — in my later professional activities. Therefore, my current field of scientific research is interdisciplinary and complementary.
Currently, the primary interest lies in combining several different phenomena to accelerate optoelectronic devices. For example, in our experiment the quantum walk occurs in a synthetic dimension generated by the electro-optical effect or the laser pump. It can introduce coupling in the chain, giving rise to continuous-time quantum walk dynamics. This system can be analogously mapped to a quantum harmonic oscillator. It demonstrates the universal character of the quantum walk comb in semiconductor lasers and, because of this, can be applied across the electromagnetic spectrum from the terahertz to the near-infrared. The variety and flexibility motivate me very much.
Yes, the research group is large and comprises about 60 employees, including PhD students. In order to work smoothly and purposefully, it is necessary to plan and monitor the work process. Therefore, twice a year we get together as a whole department. At the beginning of the year, we plan the work for the year, and at the end of the year we review the achievements: what was successful, what was unexpected, what should be explored even deeper. It is always fun and pleasant to celebrate achievements with a glass of wine and a traditional snack in the company of colleagues.
We have all capabilities except for epitaxy processes. We have never possessed the necessary technological equipment because it costs millions of euros and involves a process that is extremely difficult. So we purchase grown structures from different scientific laboratories. Mainly, we concentrate on the implementation of new concepts and the enhancement of source performance.
Only doctoral students are involved in the experiments. We do not employ master’s or bachelor’s students in our department because their knowledge is too limited, and the equipment we work with is very expensive.
Yes, such a course begins to be taught during the later years of bachelor’s studies and at the master’s level. It’s true that there aren’t many competent professors. The lectures delve into quantum cryptography, the science of qubits, as well as the physics and applications of well-developed semiconductor quantum structures.
When talking about the importance and future of quantum technologies, it is difficult to predict, but probably quantum technologies will be used in most devices. In a broad sense, many semiconductor devices operating in laboratories are already based on quantum structure technologies. As a result, devices are not only getting smaller, but also have connections between them. The future of quantum communication should be based on quantum technologies that are not only fast but also very, very precise.
My opinion about AI is twofold. I agree that ChatGPT is a good tool for conducting specialised research, but automatic application without knowledge and understanding can end in a complete fiasco. I’m afraid that some students might fail when using this tool: they will stop thinking and analysing the results of experiments, and they will stop progressing. However, the most important thing is to know when and how to use AI and to understand whether its help is important and appropriate. Keep thinking critically and creating using your knowledge. Always.
Dear Professor, I would like to thank you for coming to the Open Readings 2026 conference to encourage young scientists, those who are just starting their scientific careers. Thank you for the excellent and inspiring lecture and the short lunch spent with young people enjoying Lithuanian dishes. Thank you for the interview.
Sincerely,
Assoc. Prof. Dr. Renata Butkutė