Undergraduate student Laura Lewis, who is majoring in math and computer science, has earned a pair of national computer science awards.

In April, Lewis, a rising junior from Chester Springs, Pennsylvania, won both the qBraid Technical Challenge in the Quantum Coalition Hack and the National Center for Women and Information Technology (NCWIT) 2021 Collegiate Award. At Caltech, Lewis is advised by Elena Mantovan, professor of mathematics; Claire Ralph, lecturer in computing and mathematical sciences; and Thomas Vidick, professor of computing and mathematical sciences.

The Quantum Coalition Hackathon is a global quantum computing contest organized by Yale and Stanford, and sponsored by Google Quantum AI, IBM Quantum Computing, Microsoft, Amazon, IonQ, qBraid, and other private companies investing in the quantum computing field. There were more than 2,100 participants from more than 70 countries. Lewis, whose primary area of scholarly interest is quantum computing, found out about the contest through an email from the Caltech Physics Club and decided to check it out.

During the event, which ran April 10–11, Lewis and her fellow participants chose from a list of challenges, which they then had 24 hours to tackle. Lewis chose a problem related to Shor's algorithm.

Shor's algorithm, published in 1994 by mathematician Peter Shor (BS '81), describes how, in theory, to factor incredibly large numbers efficiently using quantum computers. It is believed that Shor's algorithm will be the downfall of RSA cryptography, a widely used secure data transmission system that creates public and private keys. The private keys are prime numbers, and the product of those two numbers is the public key. Anyone can encrypt information using the public key, but once they have, the information can only be decrypted using the private keys. The system relies on the fact that it is time consuming and computationally intensive to factor the product of two prime numbers to determine those private keys. However, with a functional quantum computer and Shor's algorithm, the process could be sped up to the point that RSA cryptography could be easily cracked.

Lewis has been studying Shor's algorithm and quantum cryptography with Vidick at Caltech's Institute for Quantum Information and Matter (IQIM), a National Science Foundation Physics Frontiers Center where researchers study physical systems in which the effects of the quantum world can be observed on macroscopic scales.

"We are currently working on quantum verification: you have a quantum computer, make it do a computation, then have a normal computer check that the computation is correct, efficiently," Lewis says. "Known protocols for this require functions with special properties, and to compute these functions, we utilize modular arithmetic, a type of mathematics that is important in cryptography. So, a large part of my work with Dr. Vidick is figuring out how to perform modular arithmetic on a quantum computer."

So far, computer scientists have been able to factor the number 15 on a quantum computer by hardcoding the modular arithmetic. "I thought, ‘OK, that seems not very good, and I'm going to try something new,'" Lewis says. She developed an implementation for a quantum computer that is not just meant to factor a single number by generalizing this modular arithmetic; in theory, she says, it is capable of factoring any number. "QBraid told me that the reason they picked me as the winner is that they'd never seen a fully general implementation of a factoring program for a quantum computer," Lewis says.

Coming off of that success, Lewis was also honored by the National Center for Women and Information Technology (NCWIT), a group she has been involved with since high school. "They have a great network for women in technology, which is important," Lewis says.

The award recognizes "technical contributions to projects that demonstrate a high level of innovation and potential impact," according to NCWIT. The application for the award included a presentation of the project to a general audience. "Presenting about quantum computing to a general audience in under seven minutes was a challenge," Lewis says.

Lewis's project was on verifiable quantum computation. Quantum computers exist, but they are "noisy"—that is, heat and electromagnetic noise can disrupt the functioning of quantum bits, or "qubits." Lewis's project, titled "Implementing Remote-State Preparation on a Noisy Intermediate-Size Quantum Device," addresses the issue of verifying that a computation performed on a quantum computer is correct.

Lewis has a longstanding interest in math and science; it started with a contest she tackled in middle school to see who could learn the programming language Python the fastest. She picked it up quickly and started learning other languages from there. In high school, Lewis was the head programmer on a robotics team and went to the FIRST (For Inspiration and Recognition of Science and Technology) Robotics World Championship. "That's when I realized that I liked programming a lot," she says.

While applying for college, Lewis received offers from 11 other universities before selecting Caltech. "It was really the Caltech Up-Close Program that convinced me to come here," she says, referring to the annual program in which prospective undergraduate students from historically underrepresented backgrounds who have an interest in math, science, and/or engineering stay overnight in the student residences, meet current students, and interact with other members of the Caltech community. "I got to know admission staff like Jarrid Whitney [assistant vice president for student affairs, enrollment and career services ] and Derek Terrell [former admissions officer]. They helped show me what a great environment there is here."

Lewis became interested in quantum computing at Caltech through one of the computer science option "pizza courses," lunchtime classes that explore a range of topics in-depth. In this one, Adam Wierman, professor of computing and mathematical sciences, explained the Caltech Information Science and Technology CS+X initiative, which leverages Caltech's expertise in computer science to advance other disciplines across campus. Specifically, he spoke about the possibilities created by the burgeoning field of quantum computing. "I thought, 'That's really interesting,' and emailed Professor Wierman, who then put me in touch with Professor Vidick," she says.

As the COVID-19 pandemic reached the United States and Caltech's undergraduate education moved online, Lewis and other students faced new challenges, including taking classes on West Coast time from her home in Pennsylvania. She looks forward to returning to campus in the fall.

"The Caltech undergraduate experience is truly one of a kind. After spending over a year away from campus, I can't wait to go back and physically be a part of the community again," says Lewis.