A paper in the latest issue of the internationally renowned academic journal Nature on quantum physics states that researchers in Germany have successfully sent quantum information through a 250-kilometer telecom network. This is the first known case of achieving coherent quantum communication using existing commercial telecom infrastructure. This demonstration shows that quantum communication can be realized under real-world conditions.
The paper introduces that quantum networks are expected to enable secure communication, such as the quantum internet. Quantum key distribution represents a theoretically secure communication technology. Exploring the coherence of light waves (their potential to interact with each other in a predictable way) can expand the scope of quantum communication, but this scalability is limited by the need for specialized equipment such as low-temperature cooling systems.
In this study, a research team developed a technology for quantum information distribution through optical fibers without low-temperature cooling. The system uses coherence-based two-field quantum key distribution, which can promote the long-distance distribution of secure information.
The authors of the paper point out that this quantum communication network covers three Deutsche Telekom data centers (Frankfurt, Karlsruhe, and Kirchheim) connected by 254 kilometers of commercial optical fibers, setting a new record for the distance of real-world and practical quantum key distribution.
They believe that this demonstration shows that advanced quantum communication protocols using optical coherence can be applied to existing telecom infrastructure.