From music to quantum physics

Celeste Carruth originally planned to be a musician. Now she is a physicist at ETH working to develop a new technique for controlling ions. As a member of the WEF’s Young Scientist community, she wants to help non-scientists better understand quantum physics.
Quantum physicist Celeste Carruth is one of this year’s WEF Young Scientists. (Photograph: ETH Zurich / Stefan Weiss)

“I was very happy to be chosen,” says Celeste Carruth right at the start of the interview. In May the US-born physicist learned that she had been accepted into this year’s class of WEF Young Scientists, which numbers just 25 researchers from around the world. The jury decided that she belongs to a cohort of extraordinary scientists who are devoted to communicating scientific findings from pioneering fields to society at large.

Since 2008, every year the World Economic Forum (WEF) chooses to integrate into its work some two dozen researchers under 40 as the next generation of academics. The WEF charges these Young Scientists to communicate cutting-edge research in an understandable way and to build a global community of scientific leaders who are committed to engaging in collaborations related to collectively identified issues.

No trip to China yet

Carruth was supposed to fly to China at the end of May to meet with other members of this year’s class, but at the WEF, too, nothing this year is happening as it has in previous years. She had to be content with attending an onboarding session online. “I hope I can do the trip sometime in the future,” she says, explaining: “Talking face-to-face with other researchers is very stimulating.”

She also had to adapt her scientific work at short notice this spring. The physicist could no longer work in the laboratory on the Hönggerberg campus, but she was able to continue working on the design for the experiment from home. “After a while, however, I got tired of always working at home and sitting in front of a screen,” she recalls. Now she’s delighted she can start to build the experiment in the lab.

Overcoming existing challenges

As a postdoc at ETH Zurich, she is developing a new technique for which her mentor Jonathan Home, Professor of Experimental Quantum Optics and Photonics, has high hopes. An ERC grant supports his team as they develop a new architecture featuring two-dimensional microfabricated Penning traps. These are expected to better control ions as quantum objects, especially in larger quantities – an important step towards using such ions in a quantum computer.

 A majority of quantum-information focused trapped ion experiments, including other experiments in Home’s group, use high-frequency Paul traps to control the ions; however this approach has a couple of serious drawbacks. For one, the ions can be arranged only in linear chains, which limits the number of quantum objects. For another, the oscillating electrical field used to trap the objects heats up the ions; this is of course unfortunate, as the ions function as quantum objects only when close to absolute zero.

Penning traps, by contrast, don’t have these drawbacks, and rely on a combination of a constant electric field and an MRI-strength magnetic field. The hope is that these microfabricated Penning traps will be able to trap the ions not only in one-dimensional but also two-dimensional structures and control them with fewer losses. It is now up to Carruth, working with other team members, to discover whether or not this will actually work as planned. “Our first step is to control two ions in a Penning trap,” she says, “after which we will steadily increase that number.”

A major shift

Carruth’s background is actually in a completely different area of physics. For her doctorate at the University of California, Berkeley, she researched antihydrogen at the ALPHA experiment at CERN in Geneva. “Our group was the first to produce a spectral analysis of antimatter,” she reports. “I thought that was very exciting: to realise that what you’re looking at is something completely new.”

However, her switch over to quantum physics was not completely unexpected. During her time at CERN, her job was to develop new techniques for controlling particles in cylindrical build Penning traps which lead to a dramatic increase in the number of  antihydrogen atoms which could be trapped and studied. It is precisely this experience that is now helping her find her footing in a completely different area. When she arrived at ETH about a year ago, it took her quite a while to fully adjust. “At CERN I was collaborating in a large group. We had shift schedules so we could take measurements around the clock, and I always had a clearly defined task.” In Home’s group, she works much more independently and enjoys more latitude. More than anything she values the wide breadth of expertise available to her at ETH. “There are a lot of smart people here,” she says.

The search for truth

When Carruth first began her studies, she had no idea that one day she would wind up working as a quantum physicist. Originally, she planned to be a professional violinist and chose to major in music at the University of Michigan. She chose to also major in physics just out of curiosity, but when she discovered opportunities to perform physics research she decided to change career paths and become a physicist. 

She still pursues her passion for the violin by playing in the Zürcher Symphoniker and occasionally plays chamber music with other scientists at ETH. A love of music is something she shares with her mentor Jonathan Home, who has also studied violin at a high level. Carruth sees many parallels between the two disciplines: “In both, if you want to be successful, you have to sharpen your senses,” she explains. “And most importantly, you need plenty of intuition.” At the YMCG music program lead by Yo-Yo Ma that Carruth attended in China this past January, the famed cellist spoke of “the search for truth in music”. That idea really resonated with her: “Physics, too, is about the search for truth – the search for what our universe is made of.”

Quantum physics becoming ever more important

Carruth has a great interest in making the mysterious world of quantum physics more accessible, which is why she is also involved in the Quantum FutureX (QFX) initiative. This initiative is still in its early stages, but is actively forming a network and developing projects that engage experts and students from different areas to work on making the fundamentals of quantum physics understandable to the public. “There are many intriguing quantum physics effects that can play an important roll in the real world,” she explains. “And with quantum technologies gaining more importance in day-to-day life, it’s important for non-experts to have a basic understanding about how they works.” She is convinced that in the near future, the CEOs of many companies will need to get to grips with this subject. “How else are they supposed to make decisions that are important to, say, the security of their company?” she asks. This is precisely where she hopes to make a difference as a WEF Young Scientist.