Stabilising nanomagnets
Researchers in the CarboQuant project embed quantised magnetic moments—so-called “spins”—in their graphene nanoribbons and then link them together. Now, the next step is enabling the use of these nanomagnets as switching elements for quantum applications in sensory technology, communications systems and data processing. To achieve this aim, the project leaders have recruited one of the world’s leading experts in the field of quantum magnetism.
“CarboQuant is the glue that connects all our research activities,” says Oliver Gröning, co-project leader. Last year, he and his colleague Roman Fasel, head of the nanotech@surfaces Laboratory at the Swiss Federal Laboratories for Materials Science and Technology (Empa) in Dübendorf near Zurich, reorganised the research groups working in their division. The new areas are carbon nanomaterials; atomistic simulations; local optical spectroscopy; molecular quantum magnetism; and material integration in circuits. The PhD students and postdocs employed in these groups now mainly work on the Carbo-Quant project. “Strong interconnections between the research groups are extremely important in our project,” Gröning says. “The new structure of our interdisciplinary collaboration is essential for making the leap from basic research to quantum applications.”
The ball is rolling
Funding from the Werner Siemens Foundation (WSS) has acted as a major catalyst in the project. “Once the ball is set in motion, it starts other balls rolling,” says Gröning with satisfaction. Thanks to the WSS grant of fifteen million Swiss francs over ten years (2022 to 2032), the project leaders are able to better link specialised subfields funded by institutions such as the Swiss National Science Foundation and the European Research Council and integrate them into CarboQuant’s long-term objective.
“CarboQuant is really branching out,” Gröning says, “also in terms of staff.” One new team member is quantum physicist Dr Yujeong Bae from South Korea, one of the world’s leading experts in quantum control of electron and nuclear spins on surfaces. Before moving to Switzerland in January 2024, Bae led her own research group at the renowned Center for Quantum Nanoscience in Seoul. Thanks to the WSS grant, the CarboQuant project leaders were able to offer her excellent employment conditions.
One of the world’s best
“Yujeong Bae was our first choice,” Gröning explains. “Her expertise is exactly what we need to achieve our goal of controlling quantum magnetism with atomic precision.” Worldwide, only a handful of people have the necessary qualifications, he says, adding that a strong motivation behind Bae’s decision to choose the CarboQuant project is likely that young scientists at Empa have a great deal of freedom in their work. “Our role as experienced project leaders is to set the general agenda, remove obstacles and open doors. But then we expect junior researchers to find their own solutions,” Gröning says. The flexibility to investigate unexpected findings and break new ground is explicitly given and encouraged: “This freedom is extremely appealing, and it opens up a creative research field that very few institutions can offer.”
Indeed, a good portion of creativity will be needed to achieve the next steps. The goal is clear: developing nanomaterials in which electron spins can be embedded and controlled in such a way that quantum operations and functionalities are viable under normal ambient conditions. This means more than connecting the spins: the researchers must also realise the controlled production of what’s known as “quantum entanglement”, a phenomenon that exponentially increases the number of possible combinations, and by extension boosts potential computing power.
Coupled, but wobbly
“We’ve already had great success in coupling the spins in our CarboQuant carbon nanomaterials,” Gröning says. Now, the biggest challenge lies in attaining the extremely transient state of quantum entanglement and then maintaining it for as long as possible. “This is what Yujeong Bae will be concentrating on.”
This is no easy task, as the spins used in the CarboQuant project are rather ambiguous creatures. It’s very possible to arrange them at specific places along the nanostructures, a process that enables controlled coupling. However, the spins are also chemically reactive, hence potentially unstable. “To stabilise them, we have to encase them,” Gröning explains. The researchers have chosen hexagonal boron nitride—white graphene—for this task. With this compound, the spins on the carbon nanoribbons can be encapsulated and protected from chemical reactions caused by factors such as humidity. This insulation, which has yet to be mastered, is the basic requirement for the next project phase: using these novel molecular nanomagnets in next-generation quantum applications such as switching elements or sensors.
