16 Juni From single photon to quantum storage
A Danish-German research collaboration is pursuing the goal of developing new quantum light sources and technologies for scalable quantum networks based on the rare earth element erbium. “One of the trickiest problems is the integration of quantum light sources with quantum memories,” says project coordinator Søren Stobbe, professor at the Technical University of Denmark (DTU). The underlying technological vision of the developers is based on the combination of nanophotonic chips from DTU with technologies from the fields of materials, nanoelectromechanics, nanolithography and quantum systems. Many different types of quantum light sources already exist today, but either they do not work in conjunction with quantum memories or they are not compatible with optical fibers.
Silicon based quantum light
According to the researchers, there is currently only one promising option: the element erbium. However, erbium interacts too weakly with light. The interaction must be significantly strengthened. This is now possible with a nanophoton technology developed at the DTU. The Helmholtz-Zentrum Dresden-Rossendorf (HZDR), which is German partner, will contribute to the development of new quantum light sources based on silicon. These light sources will operate at the same wavelengths used in fiber optic communications, making them ideal for future quantum technologies. “We want to use advanced ion beam techniques to implant erbium atoms specifically into tiny silicon structures and investigate how the use of ultra-pure silicon can improve their performance,” explains Dr. Yonder Berencén, the project leader at the Institute of Ion Beam Physics and Materials Research at the HZDR.
The implantation of a single erbium ion into a silicon-based optical nanocavity could proceed as follows: A focused ion beam delivers single erbium ions with nanometer precision, while a laser injects light into the side of a nanocavity to excite the ion. The excited erbium ion emits single photons in the C-band of telecommunications, enabling scalable quantum light sources that are compatible with existing fiber optic networks.
“This research will lay the foundation for building quantum devices that can be integrated into today’s technology,” says Berencén.
Funding and further partnerships
The Equal project (erbium-based silicon quantum light sources) is being funded by the Danish Innovation Fund with 40 million Danish kroner (around 5.3 million euros). It started in May 2025 and will run for five years. The EQUAL team also has access to other cutting-edge technologies from partner institutions: quantum networks from Humboldt University in Berlin, nanotechnology from Beamfox Technologies and integrated photonics from Lizard Photonics.
Source: www.hzdr.de
Image: B. Schröder / HZDR