A new study conducted by researchers from the Universities of Oxford, Cambridge and Manchester has made a significant breakthrough in quantum materials by finding a method for accurately engineering single quantum defects in diamond, an important step toward scalable quantum technology. The results were reported in the journal Nature Communications.
Professor Richard Curry and the Platform for Nanoscale Advanced Materials Engineering tool used to place single atoms of tin into diamond. Image Credit: University of Manchester.
The researchers used a novel two-step fabrication process to show for the first time that individual Group-IV quantum defects in diamond, tiny flaws in the diamond crystal lattice that can store and transmit information using the exotic rules of quantum physics, can be created and monitored “as they switch on.”
Researchers obtained precise control over where and how quantum features occur by carefully putting single tin atoms into synthetic diamond crystals and activating them with an ultrafast laser. This degree of accuracy is critical for developing realistic, large-scale quantum networks capable of ultra-secure communication and distributed quantum computing to address previously unsolved issues.
This breakthrough gives us unprecedented control over single tin-vacancy color centers 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.
Jason Smith, Study Co-Author and Professor, Department of Materials, University of Oxford
Specifically, the diamond defects operate as spin-photon interfaces, allowing quantum bits of information (stored in an electron's spin) to be connected to light particles. Tin-vacancy defects are classified as Group-IV color centers, which are a type of diamond defect caused by atoms such as silicon, germanium, or tin.
Group-IV centers have long been valued for their high degree of symmetry, which results in stable optical and spin characteristics, making them excellent for quantum networking applications. Tin-vacancy centers are commonly regarded as having the finest mix of these features; yet, correctly inserting and activating individual flaws has hitherto been a big difficulty.
The researchers employed a focused ion beam platform, which functions similarly to an atomic-scale spray can, targeting individual tin ions to precise places within the diamond. This enabled them to implant the tin atoms with nanometer precision, far smaller than the breadth of a human hair.
To transform the implanted tin atoms to tin-vacancy color centers, the scientists employed ultrafast laser pulses in a process known as laser annealing. This method delicately stimulates little areas of the diamond without destroying it. The incorporation of real-time spectral feedback (monitoring the light emitted by faults throughout the laser process) set this technique apart.
This allowed the scientists to detect quantum defects in real-time and change the laser accordingly, giving them unparalleled control over the construction of these fragile quantum systems.
What is particularly remarkable about this method is that it enables in-situ control and feedback during the defect creation process. This means we can activate quantum emitters efficiently and with high spatial precision - an important tool for the creation of large-scale quantum networks. Even better, this approach is not limited to diamond; it is a versatile platform that could be adapted to other wide-bandgap materials.
Dr. Andreas Thurn, Study Co-Author, University of Cambridge
Furthermore, the researchers identified and manipulated a hitherto elusive defect complex known as “Type II Sn,” gaining a better knowledge of defect dynamics and production processes in diamonds.
This work unlocks the ability to create quantum objects on demand, using methods that are reproducible and can be scaled up. This is a critical step in being able to deliver quantum devices and allow this technology to be utilized in real-world commercial applications.
Richard Curry, Study Co-Author and Professor, University of Manchester
Journal Reference:
Cheng, X., et al. (2025) Laser activation of single group-IV color centers in diamond. Nature Communications. doi.org/10.1038/s41467-025-60373-5