National Renewable Energy Laboratory (NREL) researchers Brandon Rugg, Brian Fluegel, Christopher Chang, and Justin Johnson wrote a new paper in PNAS titled "Triplet- Pair Spin Signatures from Macroscopically Aligned Heteroacenes in an Oriented Single Crystal."
The potential of quantum information science is enormous. Because of the challenges of producing units of quantum information, or qubits, without relying on extremely low temperatures, many of these applications are beyond reach. Current approaches to finding quantum materials rely on trial and error.
In the field of quantum information science, there are ad hoc methods that progress through the process. We saw a lot of that happening and decided that it was not going to suffice for a project where the goal was to limit the set of possible options. The theory gave us guidelines about what to do.
Theoreticians at the University of Colorado Boulder were enlisted by the team. Instead of searching for candidate quantum materials, they focused on designing and synthesizing molecule related to those they had studied for photovoltaics to serve as qubit candidates. A long-lived qubit can be represented by aligned spins that can be produced when excited with light. The state of the ensemble system will be changed without an added level of assembly.
It is difficult to organize the spin-based qubits in some quantum materials. A natural platform for orientation of an ensemble of spins can be found in molecules. If you want your molecule to be aligned, you need to design it in a way that it naturally organizes into assembly. Our work is different from other groups because of that.
The paper's lead author spent two years screening candidate quantum materials and fine tuning their properties.
There were a lot of factors that had to be balanced in screening the materials. It's difficult to control the position of the molecule. In partnership with our partners, we were able to get a material where all of the molecule were aligned.
Dozens of candidate materials were sent to the team by the University of Kentucky. The materials were narrowed down to a few promising candidates.
The team chose a compound that has a crystal structure in which every molecule has a common axis. The spin state of the electrons in the material was measured using time-resolved paramagnetic resonance.
The level of orientation control that we achieved with this material is difficult to achieve and not many people do it. This level of control could lead to the generation of pure quantum states which have broad potential applications.
The use of quantum computing will be important to renewable energy efforts. The Department of Energy's calls for proposals in quantum information science have spurred NREL researchers to ask how these technologies could impact the energy landscape.
It's one of the answers that quantum computing allows us to solve hard, energy-relevant problems in a more efficient way. It is going to become unsustainable if we don't develop new approaches to solve these problems. One type of unconventional computing that will help address that is quantum computing if it turns out that it's not energy intensive.
Efforts at NREL are yielding exciting results thanks to the Department of Energy's initial interest.
This is a long-term project and part of a bigger effort at NREL that we started three-and-a-half years ago, and it's the first of its kind in quantum information science here at NREL. It's a big deal to be able to publish this paper, because we were really starting from the beginning.
More information: Brandon K. Rugg et al, Triplet-pair spin signatures from macroscopically aligned heteroacenes in an oriented single crystal, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2201879119 Journal information: Proceedings of the National Academy of Sciences
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