Unlocking the Future: Germany’s Groundbreaking Quantum Internet Experiment!

Germany Quantum Internet Experiment

Germany’s Quantum Internet Experiment Sets New Global Standards

German scientists have achieved a significant milestone in quantum communications by conducting the first intercity quantum key distribution (QKD) experiment, utilizing quantum dots as single-photon sources to secure data over a 79-kilometer optical fiber link.

This advancement marks a crucial step towards more resilient quantum internet technologies, opening the door to future innovations in secure communications.

Traditional encryption methods depend on intricate mathematical algorithms and the constraints of today’s computing capabilities. However, the advent of quantum computing threatens these approaches, as they are increasingly susceptible to attacks, heightening the need for QKD.

QKD exploits the distinctive principles of quantum mechanics to ensure secure data transmission. While improvements have been made over time, expanding these networks has posed challenges due to limitations in the quantum light sources currently available.

In a groundbreaking study featured on the cover of Light: Science & Applications, a team of researchers in Germany—led by Professor Fei Ding of Leibniz University Hannover (LUH), Professor Stefan Kück from Physikalisch-Technische Bundesanstalt (PTB), and Professor Peter Michler from the University of Stuttgart—successfully performed the first intercity QKD experiment with a deterministic single-photon source.

This innovation could significantly enhance the protection of sensitive information from cyber threats.

Semiconductor quantum dots, often referred to as artificial atoms in the quantum realm, have shown immense potential in producing quantum light for use in quantum information technologies.

This achievement confirms the practicality of semiconductor single-photon sources for implementing secure, long-distance quantum internet systems.

Germany Quantum Internet Experiment: The Niedersachsen Quantum Link

Professor Fei Ding explained, “We work with quantum dots, tiny structures akin to atoms but customized to our specifications. For the first time, we employed these ‘artificial atoms’ in a quantum communication experiment spanning two cities. Our setup, the ‘Niedersachsen Quantum Link,’ connects Hannover and Braunschweig through optical fibers.”

This experiment was conducted in the German state of Niedersachsen, where a 79-kilometer fiber link connects LUH in Hannover with PTB in Braunschweig. At LUH, Alice prepares single photons that are encrypted using polarization techniques.

Bob, stationed at PTB, receives and decodes the photons using a passive polarization decoder. This connection also marks the establishment of Lower Saxony’s first quantum communication link.

Germany Quantum Internet Experiment: Achieving Stable and Secure Transmission

The research team successfully demonstrated stable and rapid transmission of secret keys over this fiber link.

They verified that positive secret key rates (SKRs) could be reliably achieved for distances up to 144 kilometers, equivalent to a 28.11 dB loss in laboratory settings. The experiment maintained a high-rate secret key transmission with minimal quantum bit error ratios (QBER) for a continuous 35-hour period, demonstrating the robustness of this link.

“Compared to existing QKD systems based on single-photon sources, our SKR surpasses all previous implementations. Even without further optimization of the source or setup, we are approaching performance levels similar to established decoy state QKD protocols that use weak coherent pulses,” remarked Dr. Jingzhong Yang, the study’s first author.

The researchers also suggest that quantum dots hold promise for broader quantum internet applications, including quantum repeaters and distributed quantum sensing.

Their inherent ability to store quantum information and emit photonic cluster states enhances their utility. The success of this experiment underscores the feasibility of integrating semiconductor single-photon sources into large-scale quantum communication networks.

The quest for secure communication dates back to ancient times. Quantum communication leverages the unique properties of light to ensure that messages remain confidential.

“Quantum dot devices emit single photons, which we control and transmit to Braunschweig for measurement. This process is at the heart of quantum key distribution,” explained Ding.

Reflecting on the success of the project, he added, “Years ago, using quantum dots in real-world communication scenarios seemed like a distant dream. Today, we are excited to showcase their potential for future experiments and applications as we move towards a quantum internet.”

Reference

“High-rate intercity quantum key distribution with a semiconductor single-photon source” by Jingzhong Yang, Zenghui Jiang, Frederik Benthin, Joscha Hanel, Tom Fandrich, Raphael Joos, Stephanie Bauer, Sascha Kolatschek, Ali Hreibi, Eddy Patrick Rugeramigabo, Michael Jetter, Simone Luca Portalupi, Michael Zopf, Peter Michler, Stefan Kück, and Fei Ding, Light: Science & Applications, 2 July 2024. DOI: 10.1038/s41377-024-01488-0

Funding

This work was supported by the German Federal Ministry of Education and Research (BMBF), SQuaD, SemIQON, the European Research Council, the European Union’s Horizon 2020 research and innovation program, the EMPIR program co-financed by Participating States, the Deutsche Forschungsgemeinschaft, and Germany’s Excellence Strategy (EXC-2123) Quantum Frontiers, as well as the Flexible Funds program by Leibniz University Hannover.