This breakthrough gives us unprecedented control over single tin-vacancy colour centres in diamond, a crucial milestone for scalable quantum devices. What excites me most is that we can watch, in real time, how the quantum defects are formed.
Professor Jason Smith, Department of Materials, University of Oxford
Using a new two-step fabrication method, the researchers demonstrated for the first time that it is possible to create and monitor, ‘as they switch on’, individual Group-IV quantum defects in diamond—tiny imperfections in the diamond crystal lattice that can store and transmit information using the exotic rules of quantum physics. By carefully placing single tin atoms into synthetic diamond crystals and then using an ultrafast laser to activate them, the team achieved pinpoint control over where and how these quantum features appear. This level of precision is vital for making practical, large-scale quantum networks capable of ultra-secure communication and distributed quantum computing to tackle currently unsolvable problems.
Study co-author Professor Jason Smith, Department of Materials (University of Oxford) said: ‘This breakthrough gives us unprecedented control over single tin-vacancy colour centres in diamond, a crucial milestone for scalable quantum devices. What excites me most is that we can watch, in real time, how the quantum defects are formed.’
Specifically, the defects in the diamond act as spin-photon interfaces, which means they can connect quantum bits of information (stored in the spin of an electron) with particles of light. The tin-vacancy defects belong to a family known as Group-IV colour centres—a class of defects in diamond created by atoms such as silicon, germanium, or tin.
Group-IV centres have long been prized for their high degree of symmetry, which gives them stable optical and spin properties, making them ideal for quantum networking applications. It is widely thought that tin-vacancy centres have the best combination of these properties—but until now, reliably placing and activating individual defects was a major challenge.
Professor Richard Curry and Dr Mason Adshead with the Platform for Nanoscale Advanced Materials Engineering tool used to place single atoms of tin into diamond. Credit: University of Manchester.
The researchers used a focused ion beam platform—essentially a tool that acts like an atomic-scale spray can, directing individual tin ions into exact positions within the diamond. This allowed them to implant the tin atoms with nanometre accuracy—far finer than the width of a human hair.
To convert the implanted tin atoms to tin-vacancy colour centres, the team then used ultrafast laser pulses in a process called laser annealing. This process gently excites tiny regions of the diamond without damaging it. What made this approach unique was the addition of real-time spectral feedback—monitoring the light coming from the defects during the laser process. This allowed the scientists to see in real time when a quantum defect became active and adjust the laser accordingly, offering an unprecedented level of control over the creation of these delicate quantum systems.
This breakthrough has several significant implications:
- Scalability: The ability to activate colour centres with a laser allows for precise placement, essential for building large-scale quantum networks.
- Integration: The room-temperature process is compatible with existing semiconductor fabrication techniques, facilitating the integration of diamond-based qubits into current technologies.
- Performance: The laser-activated colour centres exhibit excellent optical properties, including high degrees of optical and spin coherence, critical for quantum communication and computing applications.
Co-author Professor Patrick Salter, Department of Engineering Science, University of Oxford, explained,: ‘Aside from the exciting prospects the work presents for quantum technology and the science of defect investigation, it also demonstrates a new standard of feedback for laser manufacturing, where the live spectroscopic information retrieved from the machining focus is critical for successful device fabrication.’
The study ‘Laser Activation of Single Group-IV Colour Centres in Diamond’ has been published in Nature Communications.
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