Launch of eavesdrop-proof quantum communication in Ulm
- DLR and the University of Ulm have successfully transmitted a quantum key for tap-proof data transfer over their quantum network, while simulating an eavesdropping attack.
- The researchers are working together on methods and components for quantum communication and a quantum internet.
- DLR is contributing its expertise in optical communication, space and quantum technologies as well as quantum computing.
- Focus: Digitalisation, quantum technologies, quantum communication, quantum cryptography, quantum computing
The German Aerospace Center (Deutsche Zentrum für Luft- und Raumfahrt; DLR) and Ulm University have successfully started operating a joint quantum communication network. On 27 January 2025, Ulm researchers demonstrated the tap-proof transmission of computer data using Quantum Key Distribution (QKD). In this process, a 'quantum key' for encrypting and decrypting data was generated and transmitted via a fibre optic cable from the university campus to DLR and back. During the demonstration, the researchers also simulated an eavesdropping attack.
DLR and Ulm University are conducting research into advanced quantum communication. Their goal is to connect future quantum computers with a quantum internet to increase computing power at the quantum level.
Protecting data from theft and manipulation
Encryption is an effective way to protect sensitive data from theft and manipulation. This applies to personal and confidential information as well as the protection of critical infrastructures, including global data networks, energy and water supplies, and our increasingly connected and automated mobility.
In the future, a quantum computer could crack today's conventional encryption methods, which are based on binary codes made up of ones and zeros. Quantum communication provides a solution, using quantum objects to transmit information securely.
From the university campus to DLR and back
Researchers from Ulm University and DLR recently presented their joint work on Quantum Key Distribution. During the demonstration, they encrypted medical patient data and transmitted it between two computers. Among the approximately 20 guests was Ulm’s Lord Mayor, Martin Ansbacher.
The unique aspect of Quantum Key Distribution lies in the quantum key (so called because it is generated and transmitted using quantum objects), which contains the information needed to encrypt and decrypt the data. The Ulm researchers used laser light quanta, or photons, which were transmitted via fibre optics over a total distance of approximately five kilometres, from the university campus to DLR and back. The project team planned and implemented the experiment in collaboration with the company Quantum Optics Jena.
Data and keys on two channels
The sender transmits the encrypted data as a conventional binary code over a standard data network to the receiver. "The sender and receiver then jointly generate the quantum key for encryption and decryption. To do this, they transfer its information into the quantum physical states of individual photons," explains Matthias Zimmermann from the DLR Institute of Quantum Technologies in Ulm.
This process is carried out separately and securely via a quantum channel. This could be a fibre optic cable or a free-space laser link, such as those used in satellite communications. The challenge here is to transport the light through the quantum channel with minimal losses or interference.
Quantum keys cannot be intercepted
During their demonstration, the researchers simulated an attempt to intercept the quantum key. "Eavesdropping incursions are immediately detected if the data rate suddenly drops, at which point the system stops generating the key. This makes manipulation or undetected attacks impossible," explains Zimmermann. "The quantum properties of photons prevent anyone from intercepting or copying the key. Only those in possession of the original quantum key and the encrypted data code can access the data."
Quantum internet via satellite
Currently, quantum keys can only be transmitted via fibre optic cables over distances of a few hundred kilometres. Secure data transmission worldwide requires quantum communication via satellites, which in turn needs standardised procedures and certified devices.
The next step is to connect quantum computers, similar to today's internet. "A quantum internet could connect entire quantum computing data centres without leaving the quantum level during data transmission. This would significantly expand the possibilities for processing and encrypting data, for example by entangling quantum objects across multiple locations," says Zimmermann.
Key technologies for a quantum internet
The DLR Institute of Quantum Technologies is developing the key components required for quantum communication via satellite and a quantum internet, such as quantum memory and photon sources. This also includes quantum sensors, which enable more precise measurements for applications such as navigation, Earth observation, connected mobility and materials research.
Together with other research institutions and industry, DLR contributes its expertise in optical laser communication over long distances and satellite communication to numerous projects. Using these technologies, the DLR Institute of Communications and Navigation is involved in, for example, the QuNET initiative.
The development of quantum computers at the innovation centres of the DLR Quantum Computing Initiative (DLR QCI) is focussed on advancing strategically important future prospects. Through its ecosystem approach, DLR is collaborating with industry and start-ups within the QCI to develop both hardware and software for quantum computing.