optimizeD cohErent reCeiver fOr cv-qkD systEms

Program Indentification Code: QuNet+

(Funded by the Federal Ministry of Education and Research)

Duration: December 2022 – November 2025


KEEQuant GmbH (Fürth)

- Fraunhofer Heinrich-Hertz-Institute (Berlin)

- Friedrich-Alexander-University of Erlangen-Nürnberg (Erlangen)


Quantum key distribution (QKD) is one such technology and offers the opportunity for long-term security, based on the laws of quantum physics and information theory. Current QKD systems in practical implementation use a set of individual components for generating, modulating, and detecting light. This approach is cost-intensive, requires a lot of space in the transmitting and receiving units, and is difficult to scale to larger quantities. A technology from telecommunications provides a remedy: photonic integrated circuits. Similar to integrated electronics, all elements are packed onto a chip in integrated photonics, so that it can be manufactured in multiple copies on wafers. Although there are initial approaches to combine quantum technology with photonic integration, several steps are still necessary to bring both worlds together.


Goals and Procedures

In the joint project "Optimized coherent receiver for CV-QKD systems" (DECODE), a high-performance receiver for continuous variable quantum key distribution (CV-QKD) is being researched and developed. CV-QKD requires very similar components to those already widely used in coherent telecommunication technology today. To bridge the gap between these two worlds and thus achieve the state of the art in telecommunications, various components of the receiver are being further developed and optimized for QKD. This includes a photonically integrated and subsequently digital processing of both polarizations of light, as well as a broadband, and extremely low-noise transimpedance amplifier, and a CV-QKD protocol suitable for the receiver. The resulting components are tested individually, as well as in the CV-QKD system, and finally demonstrated as a complete system in the QuNet project.


Innovation and Perspectives

In the DECODE joint project, a German value chain consisting of research – components – system is being established, which will provide the building blocks for a European quantum ecosystem. The CV-QKD high-performance receiver being developed represents a significant contribution to this idea in itself and in its components and is expected to find application in the currently planned Europe-wide quantum communications infrastructure.