Caltech senior Yiyi Cai will be joining the 2025 class of Gates Cambridge Scholars at the University of Cambridge next year. Cai, who grew up in Beijing and came to the United States when she entered high school, will be pursuing an MPhil in advanced computer science.
Cai's particular interest is in quantum computing, a field she first heard about in high school. "I didn't really know how to get started then and didn't have the resources to do so," she says. "And I was pretty set on becoming a software engineer at the time. I loved computer programming."
"Once I got to Caltech, I figured this is the place for quantum computing and quantum information. This is where it was born, essentially," Cai says. "I actively searched for ways to get started in the field. Then, after my second year, Professor John Preskill [Richard P. Feynman Professor of Theoretical Physics and the Allen V. C. Davis and Lenabelle Davis Leadership Chair of the Institute for Quantum Science and Technology] decided to take me in for a summer. I'm very fortunate in that regard."
"Just being at the IQIM [the Institute for Quantum Information and Matter] at Caltech was so inspiring. There's a large group of postdocs and grad students coming in every year with very, very diverse interests, and they're just incredible people to talk to," Cai says. During a SURF (Summer Undergraduate Research Fellowship) in Preskill's group, Cai learned about the theoretical aspect of quantum information, a subfield at the intersection of computer science and physics that explores how quantum mechanics can be used to understand and build new models of computing.
"The entire premise of quantum computers is how we can use quantum mechanical phenomena to do computation. Very broadly then, it can be thought of as how nature—in the form of quantum mechanics—can be used to do computation," Cai says. "A very interesting analogy that I heard before was that if you have a bucket of water and you want to simulate its fluid mechanics, you could do so with some fancy computation on our current machines that would model all the water's movements. But what if, instead of simulating it, you just used the bucket of water itself to do the work? Now imagine that bucket of water is like a quantum computer, where the behavior of the system is the computation itself. That's the big idea behind quantum computing: letting nature follow its physical rules to process information and perform computation—and hopefully do it more efficiently."
Cai says she is pleased to have the opportunity to study at Cambridge, which has recently hired several new faculty members who work in quantum computing. "I was going to start a PhD in computer science at Stanford next year, but I'll be deferring a year for the Gates Cambridge opportunity," Cai explains. "I think I got very lucky that 2025 happened to be their 25th anniversary, so they decided to take on 25 additional scholars."
Cai hopes to use the year to explore a variety of topics so that when she returns to the United States to pursue her PhD at Stanford, she can do so with more specific aims in mind. At Cambridge, Cai will join 99 other scholars from around the world who are selected for their outstanding intellectual ability, their commitment to improving the lives of others, and their leadership potential. The Gates Cambridge Scholarship program was established in 2000 by the Bill and Melinda Gates Foundation and awards full scholarships for graduate study in all disciplines offered at the University of Cambridge.