*Professor Barbara Terhal*

### Barbara Terhal is a Professor of Theoretical Physics at RWTH Aachen University, and was a Visiting Fellow on the Mathematical Challenges in Quantum Information programme in 2013.

**When did you become first interested in mathematics and what keeps your interest fresh?**

During my school days I enjoyed doing mathematics and physics, it came naturally to me and I found a lot of satisfaction in solving puzzles. I always found physics a very deep subject about which one can never stop learning. What keeps my interest fresh is the pursuit of research that piques my curiosity and also requires me to learn and apply some new techniques or ideas.

**Could you tell us a little about your career path so far and what your current research involves?**

I started my PhD at the University of Amsterdam in 1995 in the area of theoretical quantum computation. During my PhD I spent a lot of time at IBM research in the US. After I finished my PhD in 1999, I was a postdoc at IBM, then at Caltech for a year and then became a permanent research staff member at IBM. In 2010 I felt that the time was right to move to academia and I became a professor of theoretical physics at the RWTH Aachen University in Germany.

My current research is focused on quantum error correction and its realisation in solid-state qubits. Whether and how one can realise a robust quantum memory or even quantum computer is, I believe, not just a question of engineering but one of the fundamental questions in physics today. Another more mathematical direction of my research is quantum complexity theory, which tries to formally capture the power (or lack thereof) of a quantum computer. This area of research is fascinating as it is relatively new and it involves developing quantum (matrix-valued/non-commuting) extensions of classical computer science techniques.

**What achievements are you most proud of?**

There are many achievements of which I am very proud, in particular right after I finish doing the work. When I realised that my work constructing indecomposable positive maps was indirectly related to Hilbert's 17th problem I felt very proud. I also think that my no-go results on self-correcting quantum memories in two-dimensions and my understanding of these obstructions have revealed important differences between classical and quantum information. I do not like to dwell on my accomplishments as I am more interested in thinking about the puzzles that I have not solved yet! I am also happy to let others be the judge of what is ultimately interesting or not.

**How do you achieve a balance between your work and homelife?**

I think that it is very hard to find this balance having three children myself. It is important to prioritise, to have a helpful partner, to be persistent, etc. But unfortunately there are many days that I tell myself that life would be so much easier if I did not have this drive to do science.

**What advice would you offer to young women who are just starting their careers in the mathematical sciences?**

Believe in yourself and in your own way of seeking, understanding and attacking problems, be stubborn and obnoxious. Find collaborations that work for you and avoid people/endeavours that you don't find stimulating. It is unfortunate that women form a minority in the mathematical sciences: I wish for women to achieve their intellectual goals without feeling that they have to bend over backwards to adapt to the men's world around them.

**Has your visit to the Isaac Newton Institute been fruitful?**

Yes, my visit was quite successful in getting feedback on the project that I was working on.