Quantum Leap: Scientists Boost Data Per Photon & Achieve Stable Long-Distance Quantum Communication
Scientists at the Leibniz Institute of Photonic Technology in Jena, in collaboration with international colleagues, have developed two innovative methods that may bring quantum communication closer to real-world deployment beyond laboratory confines. One method significantly enhances the amount of information that can be transmitted via a single photon; the other ensures the stability of quantum signals over extended distances. Both approaches utilize standard telecommunication components, making them compatible with existing fiber-optic infrastructure.
Quantum communication has the potential to become a cornerstone of secure data protection—for hospitals, governmental institutions, and industrial systems alike. Unlike classical technologies, which rely on electrical signals, quantum communication harnesses individual photons encoded in delicate quantum states. Its chief advantage lies in the fact that any interference with the signal immediately disrupts its quantum state, rendering eavesdropping not only detectable but fundamentally limited.
Yet, bringing quantum communication into everyday use remains fraught with technical challenges. Researchers from Germany and Canada focused on two primary obstacles: how to encode more information per photon and how to preserve signal integrity over hundreds of kilometers of fiber, despite inevitable distortions.
Their findings are presented in two scientific papers published in Nature Communications and Physical Review Letters. The former details a new photonic platform that dramatically increases the information density per photon. The latter introduces a technique for maintaining stable transmission over distances of up to 200 kilometers. Both innovations rely on conventional telecom components.
One of the pivotal advancements is the so-called time-bin encoding. Here, information is conveyed via the precise arrival time of a photon—that is, the specific temporal window it occupies. While traditional systems discern merely two intervals, the new technique expands this number to eight, thereby vastly improving data throughput. As Professor Mario Chemnitz explains, it’s akin to a cabinet of drawers: where once only one could be opened, now multiple drawers can be accessed, each containing a part of the message.
To implement this approach, researchers engineered a custom photonic chip made from silicon nitride—a material well-suited for manipulating light on miniature scales. The chip houses interferometers capable of generating and processing entangled photons, with all components drawn from standard telecom systems. In laboratory trials, the system successfully transmitted quantum information over 60 kilometers—a typical span between two network nodes.
The second challenge lay in transmitting signals over long distances without degrading quality. One of the principal obstacles here is dispersion, a phenomenon that stretches light pulses in time, making it harder to distinguish between temporal bins. To counter this, the team employed a technique based on the correlation of the total arrival time of photon pairs. Unlike conventional per-photon analyses, this parameter remains stable even under significant dispersion—marking its first successful deployment in a real communication system.
This innovation enabled reliable signal transmission over the equivalent of 200 kilometers of optical fiber, maintaining high fidelity and resistance to tampering. As Chemnitz notes, the first method allows more data to be embedded in each photon, while the second ensures that this data arrives uncorrupted. Together, they address the two core challenges in quantum communication.
These advancements are part of a broader initiative to transition quantum technologies from theoretical concepts to practical applications. The team’s mission is to make quantum communication viable using the current telecommunications infrastructure. At the Leibniz laboratory, Chemnitz leads a young research group exploring the intersection of nonlinear optics, machine learning, and neuromorphic information processing. Looking ahead, he envisions not only transmitting data via light but analyzing it directly within optical devices—technologies that could revolutionize ultrafast diagnostics and energy-efficient optical computing.
Experts emphasize that advancing quantum technologies is crucial in light of emerging threats from post-quantum cryptography. The advent of powerful quantum computers could compromise traditional encryption methods. In contrast, quantum communication offers a fundamentally new paradigm for secure data transmission—one rooted in the immutable laws of physics.
