A Danish-German research collaboration with participation of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) aims to develop new quantum light sources and technology for scalable quantum networks based on the rare-earth element erbium. The project EQUAL (Erbium-based silicon quantum light sources) is funded by the Innovation Fund Denmark with 40 million Danish crowns (about 5.3 million euros). It started in May of 2025 and will run for five years.
Quantum technology enables unbreakable encryption and entirely new types of computers, which in the future are expected to be connected through optical quantum networks. However, this requires quantum light sources that do not exist today. The new project aims to change that.
"It is a really difficult task, but we have also set a really strong team. One of the toughest goals is to integrate quantum light sources with quantum memories. This seemed unrealistic just a few years ago, but now we see a path forward," says the project coordinator Søren Stobbe, professor at the Technical University of Denmark (DTU).
The technological vision is based on combining nanophotonic chips from DTU with unique technologies in materials, nanoelectromechanics, nanolithography, and quantum systems. There are many different types of quantum light sources today, but either they do not work with quantum memories, or they are incompatible with optical fibers.
There is actually only one viable option: the element erbium. However, erbium interacts too weakly with light. The interaction needs to be significantly enhanced, and this is now possible thanks to new nanophotonic technology developed at DTU. But the project requires not only advanced nanophotonics, but also quantum technology, integrated photonics with extremely low power consumption, and new nanofabrication methods - all of which hold great potential.
HZDR will help develop new sources of quantum light using silicon, the very same material found in everyday electronics. These light sources will work at the same wavelengths used in fiber-optic communication, making them ideal for future quantum technologies like secure communication and powerful computing. "We intend to use advanced ion beam techniques to implant erbium atoms into tiny silicon structures and study how using ultra-pure silicon can improve their performance. This research will lay the foundation for building quantum devices that can be integrated into today's technology," explains Dr. Yonder Berencén, the project's principal investigator from the Institute of Ion Beam Physics and Materials Research at HZDR.
The EQUAL team has access to further technological input from partnering institutions: quantum networks from Humboldt University in Berlin, nanotechnology from Beamfox Technologies ApS, and integrated photonics from Lizard Photonics ApS.
