Nadezhda Kukharchyk | Meet the MCQSTians: they are curious about science and passionate about their research, have diverse careers paths, work in inter-disciplinary teams and are at the forefront of the second quantum revolution. In this series, we regularly feature members of the MCQST community.

"Be open-minded. Be honest. Be motivated. Try different research directions, to find the one you like the most."

Nadezhda Kukharchyk is a MCQST START Fellow. She did her PhD at Ruhr-University Bochum on fabrication and characterization of electronic spin ensembles. This is also when she discovered her passion for quantum infromation. In 2015, she joined the group of Jun. Prof. Pavel Bushev at the University of Saarland and worked on optical quantum memory and optical-to-microwave conversion at sub-Kelvin temperatures. In 2020, Nadezhda has joined the MCQST community and is currently working on development of microwave quantum memory based on optical protocols at the Walther-Meißner-Institute for Low Temperature Research (WMI). We invited Nadezhda to share her experience, current research, and motivation for fundamental research.

Can you briefly explain your research within the START Fellowship?

In my START Fellowship project, I am working on development of microwave quantum memory.

Probably, everyone is familiar with classical memory elements employed in various electronic devices. Similarly, quantum memory is a memory element to store quantum information for a reasonable amount of time and then to retrieve it on demand without loss of quantumness. Such quantum memories are in interest of realization of quantum memory networks and quantum computing systems. Type of application defines the frequency domain in which quantum communication would operate. For example, exchange of quantum information is mainly realized with optical photons in visible and infrared spectral ranges. Thus, suitable quantum memory should be resonant to optical photons of specific frequencies. The superconducting circuits on the other hand operate at the frequencies of several GHz and are currently leaders in the quantum-computing field.

Quantum memory systems suitable to these superconducting circuits are spin ensembles, like donors in silicon or rare earth spin ensembles. In numerous works, the rare earth doped crystals were implemented to realize optical quantum memory with record long storage time up to six hours. It is however extremely interesting to achieve similarly long storage times when controlling these ensembles with solely microwave frequencies.

In my START fellowship project, I am exploring the potential of rare earth spin ensembles in purely microwave frequency domain. In particular, my approach is to adapt the storage techniques, which have been successfully implemented in optics, like atomic frequency comb (AFC) and electromagnetically induced transparency (EIT), and deploy these in purely microwave frequency range.

What does your day-to-day work look like?

My morning usually starts with reading emails. The rest of the day varies: sometimes I have a day full of Zoom meetings and discussions. When I get my measurement slot in the cryostat, I mostly dedicate my time to the measurement. Since several students have joined my team, I also have everyday discussions with them. The rest of the time, I split between reading papers, processing newly measured data, writing up papers and communicating to the colleagues.

What keeps you excited and makes you want to start working in the morning?

I enjoy working in academia. My field of research is currently very seething and fast developing, which pushes one to be extremely engaged and competitive. It helps to stay motivated to compete in such rapidly growing field. However, when I find some new and exciting results in my experiments or get new challenging ideas, I get even more motivated and excited, and it is sometimes hard to take a break from work until the next day.

© C. Hohmann / MCQST

"The START Fellowship call from MCQST gave me the unique opportunity to come to WMI with my research idea and integrate it to the Institute’s research scope."

Did you always want to be a quantum scientist when you were younger?

When entering the university, I was highly motivated to go on with research. At that time, we did not have any courses purely on quantum information and quantum computing. Within the first two years, I had time to decide with my specialization and I have explored other research directions. For example, I took part in the measurement of optical spectra of the blood-cell samples in a biophysics laboratory. Eventually, I decided to specialize in physics of semiconductors and nanoelectronics, which combined fundamental courses on solid state, material science, and conductivity models as well as courses on electronics and nanoelectronic devices. I found that particularly useful for setting my path in development of computing and information research. Today, I highly appreciate this combination of fundamental and industrial knowledge. I also did an internship for two and half years in a company developing chips for satellite communication. I was motivated to get some hand-on experience in development of schematics solutions for RF circuits.

Later during my PhD, I got into the field of quantum information and found myself being keen on it. It was a huge step forward from my previous expertize, but found myself being extremely interested in it and decided to stay in this field. I however find all my previous research experience very much applicable and useful in the work I am doing today.

What drew you to MCQST?

For a while now, I was interested to collaborate with colleagues working with superconducting qubits and link those to my spin ensemble systems in experimental frame. I found Walter-Meißner-Institute (WMI) to be an ideal place for this. On one side, here there is all necessary laboratory equipment to run my experiments independently. On the other, it is possible to integrate my quantum memory systems with existing quantum computing elements in the institute. The START Fellowship call from MCQST gave me the unique opportunity to come to WMI with my research idea and integrate it to the Institute’s research scope.

What is the biggest challenge that you’ve faced so far, and how have you overcome it?

Probably, one of the biggest challenges was my PhD project. Though it seemed initially rather straightforward, it eventually required a lot of initiative on adding new experiments, establishing new contacts to perform these experiments and visiting other groups. Being at those times a very inexperienced researcher, to carry out the project successfully was a challenging task. However, I believe I was able to do it due to being strongly motivated and interested in doing research and working in academia.

"I enjoy working in academia. When I find some new and exciting results in my experiments or get new challenging ideas, I get even more motivated and excited."

Outside of science, what do you enjoy doing most?

I enjoy different outdoor activities like hiking and cycling. I appreciate very much that here you can find a great infrastructure for such activities.

If you weren't a scientist, what do you think you would be doing now?

Such “if”-questions are very puzzling as there are too many unknown variables to model an answer. If I were to have stayed longer in the industry, I would have continued to work as a hardware engineer in the private company, where I did an internship, designing various schematics solutions for satellite communication in GPS, GOLONASS and GALILEO bands. If any of my former colleagues will happen to read this, I want to convey my warmest regards to each them. In particular, to the head of my department and the head of the company for the great support they gave me with going ahead with PhD studies. Though I liked the team and work there very much, I was determined to move to science and that is why I decided to start my PhD.

What advice would you give to someone at the beginning of their science career?

Be open-minded. Be honest. Be motivated. As long as you can, try different research directions, to find the one you like the most.

Find out more about our START Fellowship and Nadezhda's research.