"Engineering is the most exciting part of research"

“I just love it when things are being built and become reality,” Cristina Benea-Chelmus says. “This chaotic state in which things are popping up and you create something!”

Benea-Chelmus feels like she’s in one of these exciting moments right now. She recently moved to Lausanne from the United States, where she held a postdoctoral position at Harvard. In January, she began her new position at EPFL as a Tenure Track Assistant Professor Microengineering at EPFL’s School of Engineering. She’s also the PI of her own lab, the Hybrid Photonics Laboratory (HYLAB), and the Deputy Director of EPFL’s Center for Quantum Science and Engineering (QSE), which was established in August 2021.

“I’m looking forward to seeing all the events we are going to organise at the QSE Center, the speakers that we are going to invite, the relations with industry that we are going to build,” Benea-Chelmus says. “And giving students both at the Master’s and PhD levels a big exposure to many different aspects in the quantum field.”

From electrical engineering to quantum engineering

It’s this enthusiasm for taking ideas and building them into tangible things that pushed Benea-Chelmus to become an engineer. When she began her studies, she was thinking about focusing in mathematics before she chose to specialise in Electrical Engineering and Information Technology, getting her BSc from Karlsruher Institut für Technologie (KIT) in Germany. In electrical engineering, she noticed that she was drawn to the simplifications engineers employ and how they are useful for treating complex systems.

“I wanted to understand more in depth how the very simple systems, which are the building blocks of these complex systems, work,” Benea-Chelmus says. “And this is when you have to go more into physics, so then I took a lot of courses in physics.”

She took courses in quantum and in solid state, which allowed her to look into the ‘black box’ of these systems and understand what they’re made of, knowledge that she could then apply in her engineering work. She did an ERASMUS exchange in Physics at EPFL and continued at KIT to get her MSc in Optics and Photonics, before going to ETH Zurich for a PhD in Physics and a postdoctoral position, and then to Harvard as a postdoctoral fellow. She was awarded a CHF 1.5 million PRIMA grant in 2021 and started as an EPFL Professor a few months later.

“For me, engineering physical systems to the point that quantum effects become tangible is the most exciting part of it, because you can use your intuition that you develop for ‘practical’ applications rather than keeping it only abstract,” Benea-Chelmus says. “And you have to find solutions in a set of parameters that has a lot of technical constraints, so you cannot think as freely as a theoretician. But, finally, you may develop something that finds applications also outside the quantum sciences, benefitting other communities.”

Hard to measure

One of Benea-Chelmus’s main research areas is in quantum metrology, the science of measuring the smallest signals in absolute values. However, this is easier said than done, because measuring these small signals involving dealing with very fragile states that do not like to be disturbed, but need to be disturbed a little in order to be measured.

“First of all, you have to remove all the noise,” Benea-Chelmus says. “Then you have to make your system very stable, and then you have to make your system very sensitive.”

At HYLAB, she will expand her focus into looking for practical ways to measure high-frequency waves, down to the quantum level. In her work, she creates links between the optical frequency and the terahertz frequency range by building transducers. Being able to transfer information between the two domains makes it easier to detect information about terahertz radiation, as there are currently not good detectors for that range.

“We transfer scientific knowledge from one discipline to another in order to create methods and technologies that neither could do alone.”

Small pieces of the puzzle

The ability to transfer scientific knowledge between disciplines and link different areas of physics is also why Benea-Chelmus is so excited to be part of the QSE Center. Her small part of the larger quantum engineering puzzle is to create photonic chips that can enable links between electronic and photonic domain. These chips have properties that are important for quantum applications as they may be made efficient for detecting single particles. This work makes use of different disciplines, such as nanotechnology and photonics.

Benea-Chelmus says she is also very happy to be part of the QSE Center because of the knowledge-sharing that takes place. “Physicists, engineers and computer scientists come together. There is a lot of know-how there on systems which are similar to the one I’m researching in their theoretical description, however physically they may be very different,” she says.

Seeing the parallels between the different systems inspires her to make analogies between them. For example, seeing how mechanical and optical systems are linked helps direct her work linking optical and electronic systems.

“Whenever you have a link, you can come up with so many new functionalities.”