Quantum communication has established itself as a reliable and effective method of ensuring absolute confidentiality by exploiting quantum properties. We reached a significant milestone with the launch of the first quantum network connecting three European countries during the G20 meeting in Trieste. A reliable quantum key distribution (QKD) link using an undersea fibre-optic cable between the islands of Malta and Sicily was successfully implemented using an innovative room-temperature single-photon detector that outperformed standard detectors. We also implemented QKD in two terrestrial free-space links in the Florence area, demonstrating that time-bin, fibre-based QKD systems can be efficiently used for free-space communications links.
Quantum communication has established itself as a reliable and effective method of ensuring absolute confidentiality by exploiting quantum properties. We reached a significant milestone with the launch of the first quantum network connecting three European countries during the G20 meeting in Trieste. A reliable quantum key distribution (QKD) link using an undersea fibre-optic cable between the islands of Malta and Sicily was successfully implemented using an innovative room-temperature single-photon detector that outperformed standard detectors. We also implemented QKD in two terrestrial free-space links in the Florence area, demonstrating that time-bin, fibre-based QKD systems can be efficiently used for free-space communications links.
Abstract Around 40 years have passed since the first pioneering works introduced the possibility of using quantum physics to enhance communications safety. Nowadays, quantum key distribution (QKD) exited the physics laboratories to become a mature technology, triggering the attention of States, military forces, banks, and private corporations. This work takes on the challenge of bringing QKD closer to a consumer technology: deployed optical fibers by telecommunication companies of different States have been used to realize a quantum network, the first‐ever connecting three different countries. This work also emphasizes the necessity of networks where QKD can come up besides classical communications, whose coexistence currently represents the main limitation of this technology. This network connects Trieste to Rijeka and Ljubljana via a trusted node in Postojna. A key rate of over 3 kbps in the shortest link and a 7‐hour‐long measurement demonstrate the system's stability and reliability. The network has been used to present the QKD at the G20 Digital Ministers' Meeting in Trieste. The experimental results, together with the interest that one of the most important events of international politics has attracted, showcase the maturity of the QKD technology bundle, placing it in the spotlight for consumer applications in the near term.
Today, quantum networks have made Quantum Key Distribution (QKD) the standard method for securely distributing encryption keys among multiple parties. In this study, we present an approach to implementing quantum networks, validated through on-field implementations. Utilizing a weak coherent pulse source, an optimized BB84 protocol (efficient BB84), and optical fiber channels, we took the initial steps within the European Quantum Communication Infrastructure (EuroQCI) initiative. Our method successfully established a quantum network linking the cities of Trieste (Italy), Rijeka (Croatia), and Ljubljana (Slovenia)-the first to connect three different countries. A second quantum link between Malta and Sicily (Italy) was established for technological characterization, while a multi-core optical fiber in downtown L’Aquila (Italy) facilitated the first QKD process involving high-dimensional quantum states in a real-world scenario.
Quantum key distribution (QKD) offers unconditional information security by allowing two distant users to establish a common encryption key resilient to hacking. Resultingly, QKD networks interconnecting critical infrastructure and enabling the secure exchange of classified information, can provide a solution to the increasing number of successful cyberattacks. To efficiently deploy quantum networks, the technology must be integrated over existing communication infrastructure, such as optical fibre links. Yet, QKD poses stringent requirements on the conditions of the network over which it is deployed. This work demonstrates the first quantum communication network in Cyprus via the deployment of a multi-node quantum network, exploiting existing commercial underground optical fibre. The network employs bidirectional occupation of fibres and wavelength multiplexing in a ring architecture to achieve, with minimal use of dark fibres, high-rate QKD. Results obtained reveal consistent key generation rates across all nodes, confirming reliable operation in a real-world environment. This deployment highlights the feasibility of leveraging existing telecom infrastructure for quantum-secured communication, marking a significant step toward scalable and cost-effective quantum networks suited for critical applications.
Quantum key distribution (QKD), in which security is ensured by physical quantum laws, is shown as the most secure communication between two distant users [1]–[3]. Recent efforts in global research focus on providing the infrastructure that can support QKD and extending applications to large scale of users and distances. Three types of links are explored up to date: terrestrial free-space links (limited by visible distance), fiber-based links (repeater-free range limited to a few 100 km [1]) and finally satellite links, which allow to bridge intercontinental distances. For each of these scenarios, different types of hardware are involved and state encoding (polarization-, time- [1]–[2], spatial- and frequency-based [3]) is tailored to mitigate link impairments. Additionally, the effort towards higher QKD rates is given [1]–[3] that future global quantum communication networks support a wider range of use cases.
One of the most advanced technologies within the field of quantum mechanics is quantum key distribution (QKD), which allows the secure generation of secret keys among remote users. In order for QKD to be more widely adopted, it must be integrated into existing classical communication systems. However, this can be difficult due to the use of various technologies and channels in deployed networks. Recently, we developed a QKD network in the metropolitan area of Padova, which connects various nodes across the city through a combination of fiber and free-space links. By utilizing a modular design based on the iPOGNAC encoder and the Qubit4Sync method, we have realized portable and adaptable systems that operate in the C and O bands. This allowed us to deploy and test the compatibility of both research and commercial QKD systems by ThinkQuantum with classical communication over a variety of links, as well as their ability to switch between free-space and fiber connections. Finally, we developed and experimentally implemented complex network configurations such as star networks, where a fiber-based transmitter and free-space transmitter could operate with a single receiver.
In-field demonstrations in real-world scenarios boost the development of quantum key distribution (QKD) towards its integration in existing infrastructures. Although QKD devices are already adopted outside the laboratories, current field implementations still suffer from high costs and low performances, preventing this technology from a large-scale deployment in telecommunication networks. Here, we present the developing of a cost-effective setup for QKD field trials, implemented for testing QKD performances in two different scenarios: (i) using an installed fiber link the metropolitan area of Florence (Italy); (ii) using a submarine optical fiber channel between Malta and Sicily.