When most people think of diamonds, words like luxury or jewelry come to mind, but researchers at the University of Luxembourg have been investigating a very different side of this material. They are exploring diamonds as a material for high-power electronics and quantum optics. By doping diamond with boron, researchers can alter its properties, making it electrically conductive.
In collaboration with other international universities, the University of Luxembourg has made significant contributions to this research, delving into its potential applications in quantum computing and biomedical imaging. For instance, Ludger Wirtz, Full Professor in Physics, Sven Reichardt, Research Scientist, Amir Hossein Talebi, Student, and Nicolò Maccaferri, Former Postdoctoral researcher at Uni.lu and now Professor at Umeå University, took part in the theory and modeling part. Their work guided the experiments and enabled the interpretation of the results.
New real-world applications of boron-doped diamond
Boron-doped diamond, a wide semiconductor, has long been studied for its electronic properties. Recently, researchers discovered a new phenomenon: the presence of inter-valence band plasmons. This means that when boron is added to the diamond, it creates tiny gaps where electrons are missing, called holes. Although scientists already understood the effects of boron doping, they hadn’t identified the connection between charge carriers and plasmonic behavior. In fact, these holes cause electrons in the diamond to move in a way that had never been observed before. This discovery could have significant implications for quantum technologies and opens the door to using diamond in new applications.
‟ The uniqueness of boron-doped nanodiamonds lies in its ability to exhibit metallic-like properties. Normally, diamond is deeply insulating and does not support charge oscillations at low energies. When doped with boron, it creates holes in the valence band and charge oscillations, or plasmons, are to be expected. But the plasmons that our experimental colleagues found had a completely different oscillation frequency than expected. Finding this frequency difference was the aim of our theoretical research.”
Full Professor in Physics
Impact on quantum technologies and biomedicine
The discovery of inter-valence band plasmons in nanodiamonds doped with boron holds significant promise for quantum information technologies. Quantum computing, quantum key distribution and quantum optics all rely on efficient single-photon emitters—devices that emit light particles one by one with well-defined energies. These photons can then be used to create entangled photon pairs, which are essential for secure communication and quantum computing.
The ability to control the diamond’s plasmonic response is particularly valuable in this context. By adjusting the energy of the emitted photons, it is possible to achieve greater precision in quantum systems. This is challenging to achieve in practice.
Another exciting application for boron-doped diamond plasmonics lies in the biomedical field. Researchers explore tiny crystal nanoparticles for medical imaging. They treat these nanoparticles with special molecules to target specific areas of the body. When exposed to different types of light—such as infrared, visible, or UV light—the nanoparticles help create detailed and precise images of them.
In short, boron-doped diamond nanoparticles have a unique advantage because of the possibility to adjust their properties. This notably improves how they interact with light, making the imaging process even more precise. “Of course, more research into the biocompatibility of nanodiamonds is necessary before any medical applications can be fully realised.”, adds Prof. Ludger Wirtz.“
The future of diamond-based quantum technologies
The theoretical work conducted by the University of Luxembourg’s team is far from over. Moving forward, they plan to explore how photons released by nanodiamonds can interact with certain vibrations in the material. These interactions could provide the foundation for optical quantum computers. However, significant work remains to be done to address issues such as decoherence, a phenomenon that can destroy the quantum properties of the system.
This work aligns with the recently funded FNR project QUANCOM, which focuses on quantum dynamics in condensed matter systems. “Collaborating with experts like Prof. Aurélia Chenu, coordinator of the QUANCOM network, we hope to refine the understanding of quantum interactions and minimise the effects of environmental interference.”, shares Prof. Ludger Wirtz.
As the field advances, further exploration of these plasmons in diamond could lead to the development of new, high-performance quantum technologies. While challenges remain, there is great potential for diamond-based materials to transform quantum technologies, and this discovery is a key step in that direction.
The University of Luxembourg collaborated with:
Giuseppe Strangi, Case Western Reserve University;
R. Mohan Sankaran, University of Illinois Urbana-Champaign;
Souvik Bhattacharya, lead author, a graduate student at University of Illinois Urbana Champaign;
Jonathan Boyd, Case Western Reserve University; Valentin Allard and Aude Lereu, Marseille University.
Research supported by the National Science Foundation.