*Professor Mary Beth Ruskai*

### Mary Beth Ruskai was a Visiting Fellow on the Quantum Information Science programme in 2004, and the Mathematical Challenges in Quantum Information programme in 2013.

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

I can't remember ever not being interested in mathematics. In college, I majored in chemistry, in part because I wasn't fully aware of the career opportunities in mathematics beyond high school teaching.

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

I took a lot of mathematics courses in grad school but earned a PhD in physical chemistry with an MS in mathematics. I had a series of postdocs in mathematical physics before finally obtaining an Assistant Professor position in mathematics at the University of Oregon. I spent most of my career at the University of Massachusetts Lowell, with numerous visiting positions at more research-oriented institutions. I took early retirement from U Mass Lowell in 2002 and was a part-time Research Professor at Tufts University from 2003-2013 supported only by grant funds (and visiting positions elsewhere). I will turn 70 in February 2014 and am beginning to ease into more retirement.

My current work is in quantum information theory (QIT). My research has always focussed on mathematical problems in quantum theory. I did my thesis on a mathematical question of interest to quantum chemists. As a postdoc I solved an important question in mathematical physics about entropy, but physicists weren't interested then, so I moved into Schrödinger operators, studying mathematical questions about atomic and molecular Hamiltonians. In about 1997 people in QIT started asking about my old work on quantum entropy and I moved into that area. Then in about 2005, people in QIT obtained the first new results in over 30 years about the quantum chemistry problem I'd done my thesis on. I feel that I've come full circle.

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

- Co-authoring the proof of the Strong Subadditivity of quantum entropy
- Proving that an atom with fixed nuclear charge can bind only finitely many electrons
- Working with young people in QIT to use quantum error correcting codes to solve a 40 year old open question related to my thesis
- Organising the 1990 CBMS conference on wavelets at which Ingrid Daubechies was the principle speaker; organising the 2010 programme at the Mittag-Leffler Institute in Stockholm; and organising some very successful interdisciplinary workshops in QIT
- Becoming a winter leader for the Appalachian Mountain Club
- Continuing to do easier hiking and skiing after 3 joint replacements
- Challenging the US TSA's policy of invasive pat-downs of people with metal implants

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

I find the wording of this question problematic, as it seems to assume a traditional lifestyle with family and children. This is not the only option.

I moved from Oregon to Boston, because I found single life difficult in a small college town. Although I very much enjoyed hiking and skiing in the mountains nearby, it was hard to find people to go with.

In Boston, I found it easier to connect with other people to hike and ski (although the mountains were smaller and farther away). I also joined a women's squash team where I was able to connect with other women professionals.

I often think that my *family* is spread across the world with the many friends I've made during the course of my work.

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

Everyone has to find their own path. Use every opportunity to make connections at research conferences and workshops!! Don't undervalue teaching - it can be very rewarding and improve your own understanding.

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

My first visit in 2004 was extremely fruitful.

The second in 2013 was marred by some health problems. However, the opportunity to connect with some collaborators was still very helpful.