Universidade de Vigo
Grupo de Antenas y Radar

Grupo de Antenas, Radar y Comunicaciones Ópticas

We are a leading research group in the area of electromagnetism. Our scope covers antenna design and measurement, computational electromagnetism, EMC, radar, millimiter waves applications, electro-optics and quantum information technology.

Quantum Technology for Secure Optical Communications

As computer networks spread worldwide with users accessing them via millions of different terminals, secure data transmission and data storage become more and more relevant. To guarantee these goals, it is necessary to develop new methods and techniques.

One of the most important problems in modern cryptography is the transmission of secret information from a sender (usually called Alice) to a receiver (Bob) over an insecure communication channel. The goal is to guarantee that any possible eavesdropper (Eve), with access to this channel, is unable to obtain useful information about the message. Secret systems have previously been studied from an information-theoretic perspective by Shannon, who analyzed a scenario where Eve has always access to exactly the same information as received by Bob. In this situation, Shannon proved that every perfectly secret and uniquely decodable system requires that Alice and Bob previously share a secret key of, at least, the same length as the message to be transmitted.

Quantum Key Distribution (QKD) is a novel technique that exploits quantum effects to establish a secure secret key between two distant parties. This secret key is the essential ingredient of the one-time-pad or Vernam cipher, the only known encryption method that can provide information-theoretic secure communications. QKD is the prime example of ideas in Quantum Information Theory that use fundamental laws of quantum physics to accomplish tasks that cannot be achieved by purely classical means. It differs from classical key distribution schemes since in QKD one can actually prove the unconditional security of the final key.

QKD is available with today’s technology, and has already entered the market to offer efficient and user-friendly systems providing an unprecedented level of security. Current QKD devices use simple quantum mechanical states of light such as weak coherent pulses transmitted through optical fibers. While classical cryptographic methods are still safe enough for short-lifetime encryption, quantum cryptography may prove valuable with respect to the provision of unconditional security, not only now, but also, in the long-term. Even QKD with very low bit rate (for instance, hundreds of bits per second) may significantly improve the security of contemporary cryptosystems.

More information about practical QKD and the kind of security this technology  provides can be found, for instance, in the following document from the "Updating Quantum Cryptography and Communications" project.

Our main interests in this field include closing the gap between theoretical concepts for QKD and their experimental implementation with current technology, as well as the development of new methods that will allow us to increase the secret key rate and maximal distance covered by practical QKD systems.

The group participates in the recently created Quantum Information Network in Spain

For more information, please contact Prof. Marcos Curty.