Complex models for the global quantum internet

Security and privacy in the transfer of information through the internet is one of the major concerns that individuals, businesses and even administrations have acquired these past years.

Today, we have a new way of sharing information that deals with massive and exponentially incremental data creation and storage as well as data traffic at global scales, in most cases, driven by new fast-growing technologies such as the Internet of Things, Big data, virtual reality, autonomous vehicles and other applications of artificial intelligence. Many of this information, e.g. related to health, finance or even defence-related communication, is extremely sensitive and needs to be handled with protocols and procedures that ensure the highest degree of security.

Present day cryptography implemented to secure such information is potentially in danger due to the advent of quantum computers, which will have the power to instantly break most methods currently considered secure and widely used. Thus, quantum cryptography brings new methods, systems and protocols that cannot be broken even by quantum computers. It relies on the defying properties of quantum mechanics to achieve the most secure form of communication known, impossible to intercept without detection.

So far, many scientists are working on developing quantum communication networks for the future quantum internet, which will include quantum processors interconnected by quantum channels, which can, among other things, will distribute private messages using quantum cryptography, distribute entanglement, and allow the users to perform blind quantum computation on the cloud. It is foreseen that this network will be a game changer in the communications arena.

In a recent paper published in PRL and selected as cover image of the journal, ICFO researcher Daniel Cavalcanti and co-authors from the International Institute of Physics in Brazil use network theory techniques to study a quantum internet based on optical fibers, and characterize its connectivity properties. Among other things, their simulations show that the quantum internet model displays a phase transition between a disconnected and a highly-connected phase, with the density of nodes being the order parameter.

The results of the study serve as a benchmark for the development of a quantum internet, for example in providing information of the minimum density of nodes needed to have a fully connected network and for the average distance between nodes, or to distribute entanglement accross the network more efficiently.