Quantum careers: Building tomorrow’s quantum computers, teaching tomorrow’s scientists

Sergio Cantu lives in Massachusetts, but this spring he is in Tokyo, where he and his colleagues are unpacking quantum computer parts that they’ve sent across the ocean. The core of the computer is a small glass cube filled with 30 grams of neutral rubidium atoms, 260 of which will serve as qubits at a time. “You hope that things didn't shake too much during shipping,” says Cantu, the vice president of quantum systems at QuEra, a Boston-based quantum computing startup.

Cantu’s team is building the quantum computer at Japan’s National Institute of Advanced Industrial Science and Technology. There, researchers will use the machine to develop quantum algorithms and work to integrate it with the institute’s supercomputer. “It has been an opportunity of a lifetime,” says Cantu, also an APS member.

This isn’t Cantu’s first international experience. Born as an American citizen in Texas, Cantu moved across the border as a child to Tamaulipas, Mexico, when his father got a job as state postmaster general. After attending high school in Mexico, he returned to the U.S. to study physics, first at the University of Texas at Brownsville, and later at the Massachusetts Institute of Technology for his Ph.D. “I always knew I wanted to do experiments,” he says.

As a student, Cantu worked on instruments for gravitational wave detection for the LIGO collaboration. That led him to an interest in optics and lasers. In graduate school, he studied and built devices to study quasiparticles called Rydberg polaritons formed from atoms and photons, which paved his way toward his current job building quantum computers.

After earning his Ph.D. in 2021, he began working at QuEra, which had fewer than 10 employees at the time. The company has grown to a few dozen employees, with plans to expand to 130 by the end of the year.

But the path hasn’t been easy. He found it particularly difficult to navigate the American higher education system, as someone who grew up outside of it. “It was just not very clear,” he says. “How do you apply to college? How do you apply to do science? What's a Ph.D.? How do you apply to a Ph.D.? What's a GRE?”

These gaps became evident when Cantu applied to attend university in the U.S. For the first application, he sent his awards and medals he’d received, along with the original and only copy of his high school diploma, to a university. In Mexico, universities commonly ask for original copies as a measure against fraud. “I thought that I would get them back to send to the next school,” he says. “I kept waiting and waiting.”

He finally contacted the university, which returned his materials. He had enough time to apply to other schools, but it was a stressful lesson to learn.

In graduate school at MIT, Cantu wanted to find a way to share his knowledge of American universities with other Mexican students. He found that opportunity in a new nonprofit named Clubes de Ciencia.

Clubes for short, the group organizes weeklong science workshops for high school students and undergraduates over the summer in multiple cities in Mexico. For each workshop, they pair a Mexican academic with a non-Mexican academic as instructors to teach subjects ranging from physics to biology to climate change. “We want to empower and inspire a new generation to pursue a career in science and technology,” says Carla Marquez-Luna, a geneticist and a current co-director of the nonprofit. Clubes has about 100 volunteers and one full-time and one part-time employee.

Cantu joined a few months after the group formed in 2013. The program has taken off. Since then, Clubes has hosted more than 7,500 students in Mexico, 51% of whom are women.

The workshop began in just one city in Mexico, Guanajato, and now operates in 10. Cantu started the workshop in Monterrey, which is near where he grew up. “Because I'm from the border, I wanted to have an option in the northeast of the country,” he says. Clubes has also expanded to seven more countries, including Brazil, Colombia, Bolivia, and Spain.

The workshops emphasize hands-on activities. Cantu, for example, has taught workshops on laser encryption, where students build their own lasers using diodes and Raspberry Pis. In 2023, he taught his students to perform experiments using Aquila, a QuEra-built quantum computer available on the cloud that he named and helped to build. The interactive approach contrasts with his early science education in Mexico, where the curriculum prioritized textbook learning. “I didn't see a multimeter until I got to college,” he says.

The workshops have given Cantu the opportunity to mentor students from a similar background. In 2015, Grecia Castelazo met Cantu when she attended Clubes de Ciencia in Monterrey as a high school sophomore. Having participated in international physics competitions, she knew she was interested in physics and sought Cantu for advice.

Cantu excels as a science communicator, says Castelazo. “He finds the language to make a lot of these concepts accessible, and he’s just very kind,” says Castelazo. “I'm sure there's a million computations going in his head, but when you talk to him, he’s so calm.”

Cantu’s example made her ambitions of studying physics at a U.S. university more real. “He had already gone through the things that I wanted to do,” she says.

Castelazo got into MIT in 2017. In 2019, Cantu recruited Castelazo to work as a teaching assistant for that summer’s Clubes workshop in Ensenada. Now, Castelazo is a first-year Ph.D. student at the University of California, Santa Barbara, studying quantum algorithms for near-term machines — perhaps future upgrades of the machine that Cantu is installing in Japan.

For Cantu, cultivating community has always been part of his scientific career. Prior to his work in Clubes, as an undergrad member of APS’ Texas Section, he would travel around high schools in Texas performing demos in a show called The Physics Circus. And now in Japan, he’s met a new group of people excited about physics. “The Japanese community has been very welcoming,” he says. “It’s nice to work in an environment where people are excited about what you're doing.”