Quantum technologies can be applied on a standard telecommunications network

Spain has achieved experimental success, for the first time, operating a quantum cryptography network integrated in commercial optical network through technologies based on Software Defined Networking (SDN), allowing for the implementation of quantum and classical network services in a flexible, dynamic and scalable manner.

The network uses an infrastructure of fiber provided by Telefonica Spain that connects three ofits facilities located in the metropolitan area of Madrid. The trial has been ongoing since last May and a preliminary report has been recently presented at QCRYPT2018, the largest conference in the field.

The network integrates Quantum Key Distribution (QKD) devices developed by the Huawei Research Lab in Munich, in collaboration with the Center for Computational Simulation (CCS) at the Universidad Politécnica de Madrid (UPM) through the Research Group in Information and Quantum Computation at the Computer Sciences school (Escuela Técnica Superior de Ingenieros Informáticos).

The network’s SDN-based management modules have been developed by Telefónica’s GCTIO Network Innovation team and the components required for integration of quantum cryptography have been developed by CCS with SDN and network function virtualization (NFV) technologies.

Integrating all of these elements has made it possible to demonstrate that QKD techniques can be applied in a real production environment, combining the transmission of data and quantum keys over the same fiber.

The management of the quantum and classical channels is done in an integrated way through SDN techniques, sharing the optical network in an optimal way. The fact that this has been developed on an existing infrastructure using standard communications systems highlights the maturity of this technology, which allows switching between links connecting points that may be up to 60 kilometers apart.

This technology is also capable of having more than twenty channels sharing the same fiber in the same optical band that uses the quantum channel, allowing the simultaneous transmission of quantum signals with more than two terabytes per second of data in metropolitan area networks when using standard 100 gigabytes per second modules.

An advanced security quantum solution

Secure communications are based on the use of cryptography, in which information is encrypted using a secret key. Only the users who know the decryption key can access the secret messages. The cryptographic techniques currently in use to exchange keys or electronically sign documents are based on mathematical problems that need too much time to solve. However, as computing capacity increases, the time to solution is reduced, along with the security of these methods.

To avoid this problem, the size of the keys has had to increase as computing capacity has grown. These techniques may be rendered completely obsolete with the emergence of quantum computers that, using the principles of quantum mechanics, can solve presently intractable problems. These include breaking the keys generated by the most used cryptographic methods, making the majority of the communications security infrastructure useless.

Nevertheless, quantum technologies offer a solution to the vulnerability of current methods. With these technologies it is possible to apply quantum principles to generate a secret key through a public communications channel, so that the key is secure against any attack, including one from a quantum computer. Quantum technology even make possible for any attack attempt to be immediately detected.

Quantum technologies

Quantum Key Distribution is one of these technologies: not only does it solve the problem of the threat posed by quantum computation to cryptographic key generation algorithms already in use, it can also provide a much higher level of security. QKD requires a physical infrastructure of optical fibers, such as that provided by Telefónica Spain used to connect the communication centers in the pilot program.

Until now, the viability of QKD has been demonstrated in laboratories and in controlled field trials (such as the one carried out in 2009 by Telefónica and the Research Group in Information and Quantum Computing that exchanged keys through a metropolitan optical fiber ring network), but there have always been problems with the ability to deploy it on a commercial infrastructures and to integrate it with the operating mechanisms of such a infrastructure. This experience demonstrates that it is possible to overcome those obstacles.

In the network a new quantum technology has also been used for the distribution of quantum keys based on “continuous variables” QKD (CV-QKD) that is more compatible with classical technologies than existing ones. The combination of these technologies has enabled a complete integrated network of classical and quantum communications.

The deployment over an existing communications’ infrastructure and the use of standard telecommunications systems that has been achieved in this trial is the first of its kind, demonstrating this technology’s capacity for real-world use.

Network convergence

“The ability to use new network technologies like SDN, designed to increase the flexibility of the network, together with new QKD technology is what allows us to really converge quantum and classical networks on the existing optical fiber infrastructure. Now we have, for the first time, the capability to deploy quantum communications in an incremental way, avoiding large upfront costs, and using the same infrastructure,” explains Vicente Martin, head of the Center for Computational Simulation and responsible for the team at UPM that participated in this trial, as well as member of the R&D program of activities at the Community of Madrid in Technology QUITEMAD+CM.

Momtchil Peev, Huawei Project Leader of the Quantum Communication Project in Munich adds as well: “The test CV-QKD devices that we present here have the inherent CV advantages: they do not need (ultra) low-temperature (bulky) Single Photon Avalanche Detectors and can (potentially) reuse classical optical coherent communication technology. Moreover instead of addressing performance records alone we have chosen a flexible design focusing on control and key delivery interfaces, showing the feasibility of more seamless future integration into modern networks.”

María Antonia Crespo, Director of Transport and IP Connectivity in Telefónica Spain also points outs: “Telefónica Spain’s optical network, in combination with our high-capacity photonic transmission systems, offer the required performance to provide secure channels based on quantum communication. This enhanced security is a key enabler for next generation networks, flexible, virtualized and software-defined.”

Diego R. Lopez, Head of Technology Exploration & Standards in Telefónica’s Global CTIO Unit, concludes: “We have been working to develop a field trial that demonstrates the provision of secure communication services based on QKD using a commercial SDN-managed optical network infrastructure.”

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