Young scientist applies good old problem-solving skills to quantum computing



In this series, NUS News profiles the University’s Presidential Young Professors who are at the forefront of their research fields, turning creative ideas into important innovations that make the world better.


As a primary school girl, her favourite pastime was soldering electronic circuit boards in her father’s workshop at home.

Twenty-five years later, she is designing superconducting “circuit boards” for quantum computers as well as leading and inspiring an international group of young researchers in her own laboratory at the futuristic Centre for Quantum Technologies at NUS.

Assistant Professor Yvonne Gao’s scientific quest is supported not only by the NUS Presidential Young Professorship that she received in 2020, but also by Singapore’s National Research Foundation Fellowship. She has also been named one of Women’s Weekly’s Great Women of Our Time and one of the MIT Tech Review’s Innovators under 35 (Asia Pacific). In 2021, she received the prestigious Young Scientist Award which recognises young researchers, aged 35 years and below, who are actively engaged in R&D in Singapore, and who have shown great potential to be world-class researchers in their fields of expertise.

Asst Prof Gao’s lab is exploring techniques to split quantum computers into modules interconnected by superconducting circuits. This makes the system much more flexible and robust to failures.

So far, most quantum computer prototypes work as a single CPU, which uses principles of quantum mechanics to perform large, memory-intensive calculations many, many times faster than regular computers. While a traditional computing bit is in a state of either 1 or 0, a quantum bit can be both at the same time.

Asst Prof Gao designs the modules using aluminium blocks precision-machined with polygonal patterns cooled to near absolute zero - more than 270 degrees below freezing. The centrepiece of her lab is the fridge. It uses helium-3 and helium-4 isotopes as the coolant and is not meant for ice cream and soda.

However, she quickly dispels any notion that quantum mechanics is a geeky subject studied by weird scientists. “It’s just like what anyone would do in any working environment - we’re solving problems. The problems are of a scientific nature just because of our choice. We need specific background knowledge but the problem-solving skills apply to any profession.”

Her work could eventually improve people’s lives in many different ways, for instance, it could give a boost to data science and artificial intelligence that are vital to Singapore’s Smart Nation drive. In fact, this is one of the key foci of both NUS and Singapore’s Research, Innovation and Enterprise 2025 plan.

A journey full of fun

Asst Prof Gao first found her “true love” in secondary school. She had three suitors - biology, chemistry and physics. She had a hard time with the first two, having to memorise lots of things from chemical formulas to taxonomic names to metabolic pathways.

But she loved physics lessons. Her teacher explained physics principles using analogies with everyday phenomena. “I didn’t like memorising things. For physics, I felt like once I understood it, I could deduce a lot of things rather than memorising a name that you just have to know,” she said.

Her enthusiasm in her studies earned her two of Singapore’s National Science Scholarships for her undergraduate and PhD studies.

When Ms Gao first arrived at the University of Oxford, she struggled to focus. She was experiencing a freedom she never had before. There were speeches by prime ministers, there were street protests about tuition fees, and many other things going on.

And of course, there were the English pubs. She hung out often with the other physics students at her college, three of whom were girls. She was the only one among them who would continue in physics research, while the rest went on to successful careers in other sectors. “It really shows the value of a physics education - it prepares you for whatever you want to do after,” she said.

By her second year Ms Gao had gotten the hang of it. Her course was highly conceptual, so for her project, she bought some “random” parts on eBay and assembled her own heat detector. She invited her classmates to walk in front of it during the presentation to demonstrate its functionalities.      

It was at Oxford that she first got “entangled” in quantum mechanics, inspired by her college tutor who was a specialist in the field. That would ultimately take her across the Atlantic to Yale University, where she joined the lab of Professor Robert J. Schoelkopf and embarked on her journey of exploration and discovery of superconducting quantum circuits.

“It was a really old building,” Asst Prof Gao said. “When I first started going to the lab, it felt overwhelming because there were so many instruments I had never seen before, there were so many people discussing things and using terms I had never heard of. I got worried about how steep the learning curve would be.”

But she quickly caught up and was soon talking the same jargon as everyone else. In fact, after a very exciting and intense first year in the lab, she decided to recharge by embarking on a six-week trek to Everest Base Camp.

Just before she left for the hike, she was working on a project on how contaminants and defects in a thin film affected the operation of a quantum device. The system was behaving weirdly and no one knew what was going on.

It might seem like the worst time to “abandon” the lab, but the cool and crisp air of the Himalayas cleared Ms Gao’s head, and she returned feeling invincible with a renewed vigour and confidence in solving any scientific problem. After further investigation, the team finally discovered that a previously undetected magnetic field was the culprit, and now it took their research in a new and even more interesting direction.

During her time at Yale, her friends introduced her to the sport of bouldering - another activity that let her do her favourite thing, problem solving. In fact, climbers often refer to finding a route up a rock face as “solving” a “problem”. She also met a French physicist who would become her husband.

Nurturing a team of problem-solvers

Today, Asst Prof Gao makes it clear to her team that it is completely fine to make mistakes. Without mistakes, one may not even realise there is a problem to be solved. “That also makes the whole process a lot more fun because people are not afraid to try new things,” she said. “Even if it fails or does not come to anything, you learn something from it.”

To ensure her lab has the best possible problem-solving capabilities, she picked a cosmopolitan mix of theoreticians and experimentalists from six countries across the globe. She has an electrical engineer, a materials scientist and a traditional physicist in her team. Some came with no idea of superconducting quantum circuits. But collectively, they brought the diverse skills needed to solve unanticipated problems.

When COVID-19 hit, Asst Prof Gao and her team could no longer get together for regular meals and leisure activities the way they used to. But they have found ways around it, like having online dinners to chat about everything scientific and non-scientific, and playing board games online.

Meanwhile, she is managing her time between the lab and a new family life, having had her first child recently. And that gives her the ideal state of mind to nurture her lab like a family - one that talks heart to heart when it comes to tackling their next great scientific challenge, whatever it may be.

More Proof of Passion stories here.

The NUS Presidential Young Professorship (PYP) scheme supports talented young academics with excellent research track records in advancing their cutting-edge research. More information about the PYP scheme is available here.