A Cal Poly research team is working on one of the final steps to build the world’s first large-scale quantum computer.
If the results turn out as expected, physics assistant professor Katharina Gillen’s research could be the missing key.
“It would just be awesome if somehow I could provide one piece of the puzzle,” Gillen said. “Many people have more resources than I do, but I could provide just this one piece of the puzzle that helps the community solve these problems, in our case building a quantum computer.”
A quantum computer is an instrument that can perform large operational tasks on data much faster than a classical computer.
Researchers are still looking for a way to store large amounts of information in quantum bits in order to someday build a quantum computer that can be used for practical purposes. It has been established among other researchers that using neutral atoms in light could work for quantum computing, but finding a way to trap those atoms is the issue. There are general ways to trap atoms, but many of them cannot be used to trap the thousands needed for a quantum computer, Gillen said. That is the focus of Gillen’s project.
“I’m hoping to simply show that you can fill these traps with atoms,” Gillen said. “Once I’ve done that, I want to confirm what I have calculated in terms of how well they trap the atoms and confirm that they could be used for quantum computing.”
Gillen’s goal is to prove atoms can be loaded into a tiny circular pinhole trap. Lasers with light and dark spots would shine on the pinhole — these light and dark spots minimize decoherence. If this can be done, someday it might be possible to isolate single atoms into a sequence of traps to create an array of qubits, or units of quantum information. The lasers would then be able to alter the atoms in order to make computations, based on factors such as the amount of time they hit the atoms, she said.
“We can measure what the light pattern looks like, and so we did confirm that that looks like what we calculated and so we’re pretty certain that the atoms will react to it the way that we think, but it is a big deal to actually prove that,” Gillen said.
Although the device can be called a cold atom trap, it actually has little to do with temperature, Gillen said. Trapping the atoms instead slows them down, so they can be used in certain experiments. The technical term for the device is a magneto-optical trap, in which a magnetic field and lasers work together in a process that collects and slows the atoms.
Magneto-optical traps have been built by other research groups before, but each has been used in different experiments for trapping atoms, Gillen explained.
“A lot of work goes into just the lasers and keeping them at that specific frequency,” Gillen said.
Depending on factors such as time constraints and unpredictable complications, it will take approximately another year to see results, Gillen said.
A total of 16 students have worked on the project over five years, with majors ranging from physics, mathematics and chemistry to mechanical and electrical engineering. Involvement of engineering students is an important component because they help build and maintain the entire trap structure, Gillen said. Mechanical engineers help build specialized parts, while electrical engineers help design, build and fix electronics.
Mechanical engineering graduate student Bert Copsey started working on the project after he took a physics class taught by Gillen. Gillen told the class about her research and invited students to get involved. Copsey has worked with Gillen for four years now, mostly writing codes, building parts for the trap and tuning lasers. He said he also went to the Division of Atomic, Molecular and Optical Physics conference in Pennsylvania at the end of his second year to present research on the magneto-optical trap.
“That was a really cool experience,” Copsey said. “I was presenting the research we’ve been doing to a whole bunch of really big important physicists.”
Copsey said working on the project has helped determine his career path.
“I’m in engineering because I thought I wanted to be an engineer as a kid, but it turns out I kind of want to be a physicist,” Copsey said.
Sara Monahan, a physics senior, also got involved with the project through a class taught by Gillen. She learned theoretical knowledge in the class, and began to work on the experiment over this past summer.
“It’s been one of the best experiences of my life,” Monahan said. “Being able to feel like I have an actual purpose as a physics major, like I’m actually doing productive things, has really made a difference. I’ve gained a lot of knowledge and I’ve gained a lot of confidence because I got to learn how to apply the knowledge.”
In addition to conducting meaningful research in her field, Gillen said interacting with students is an important and enjoyable element of her work.
“Of my entire job, that’s just the (most fun) thing, is working so closely with individual students on this project, and watching them learn,” Gillen said. “They’re basically learning skills that I learned in grad school. I’m glad I get to be a part of that.”
If Gillen does achieve the results she is expecting, it will warrant a publication in a research journal, which would bring positive attention to Cal Poly and help attract follow-up funding, she said.
“It will kind of make us famous,” Gillen said. “It would put Cal Poly on the map, professionally speaking.”