Researchers have achieved a groundbreaking 120km quantum key distribution, demonstrating secure communication over unprecedented distances. Their work, published in Phys. Rev. Lett., enables simultaneous transmission of quantum-encrypted data and classical signals. The breakthrough advances practical quantum networks, overcoming key challenges in long-distance secure communication.
Advancements in Continuous-Variable Quantum Key Distribution
Researchers continue to refine continuous-variable quantum key distribution (CVQKD) as a viable method for secure communication. According to a recent study by Adnan A. Hajomer, Ivan Derkach, Vladyslav C. Andersen, and Tobias Gehring, scientists have now demonstrated CVQKD across 120 kilometres of optical fibre. This achievement represents a significant step forward, pushing the distance limit for this quantum communication technique.
Building on this success, the team suppressed interactions between quantum-secured data and classical data travelling through the same fibre network. Unlike previous experiments requiring additional optical filters or network modifications, this breakthrough utilised a built-in filter inherent to the CVQKD setup itself. The researchers then optimised the transmission of the quantum-secured data, enabling the 120km transmission even while the fibre was fully loaded with classical data traffic.
This demonstration by Hajomer, Derkach, Andersen, and Gehring has essential implications for integrating quantum security into existing infrastructure. CVQKD encodes random numbers in the amplitude and phase of light waves, alerting parties to potential eavesdropping. Successfully combining this with standard data transmission over long distances moves CVQKD closer to practical, large-scale deployment within current fibre-optic networks.
Overcoming Distance Limitations in Quantum Communication
Building on this achievement, researchers at Palacký University Olomouc and Denmark demonstrated a key improvement in coexisting quantum and classical data transmission. They successfully transmitted quantum-secured data alongside standard data traffic across 120 kilometres of optical fibre, a significant leap beyond previous limitations of a few tens of kilometres. This breakthrough hinged on suppressing interactions between quantum and classical signals, enabling greater distances without compromising security.
The team achieved this suppression not through complex filtering systems, but by cleverly exploiting a built-in filter already present within the continuous-variable quantum key distribution (CVQKD) setup itself. According to Vladyslav C. Andersen, optimizing the transmission of quantum-secured data within this existing framework proved crucial. This approach avoids the need for costly or disruptive upgrades to existing fibre networks, making wider implementation more feasible.
This extended range has significant implications for practical quantum communication networks. The ability to securely transmit data over longer distances without specialised infrastructure lowers the barrier to entry for organisations seeking to protect sensitive information. Adnan A. Hajomer notes that this advancement brings the prospect of a fully integrated quantum internet, alongside current classical networks, one step closer to reality.
This 120km demonstration by researchers at Palacký University Olomouc and in Denmark represents a significant step towards practical, long-distance quantum communication. The implications extend beyond securing data, potentially enabling the integration of quantum key distribution with existing fibre-optic networks. For industries reliant on secure data transmission, like finance and government, this development could enable more robust defences against future quantum-based cyber threats.
Building on continuous-variable quantum key distribution, this achievement overcomes a critical distance limitation, paving the way for wider deployment and real-world applications of quantum-secured communication infrastructure.
