What’s New in Quantum Communications: Key Distribution System for Ten Participants

A group of physicists presented a system of quantum key distribution for ten participants – for a long time their number did not exceed two. Let’s tell you what is known about the development and analogs.


A photo – Shahadat rahman – Unsplash

In quantum networks, data is transmitted over fiber optic channels using polarized photons. Photons are very fragile and are destroyed when read. In theory, this property protects quantum communication channels from eavesdropping; therefore, their use for distributing cryptographic keys between classical computing systems is considered a rather promising solution.

At the same time, the implementation of such systems – even at the level of scientific laboratories – cost a lot and do not allow achieving high transfer rates. For the most part, they use a simple point-to-point format, using repeaters and trusted nodes to read the encoded data and send it down the chain. This approach – with the introduction of a large number of intermediate elements – writes off some of the declared advantages of the system from the point of view of information security, complicates the structure and process of network deployment.

In August, a group of physicists from South Africa presented an alternative mechanism for quantum key distribution. It allows you to establish an exchange between ten participants and does not require repeaters.

How it works

For this project, engineers proposed to move away from classical coding approaches in quantum key distribution systems and transmitted cryptographic information using orbital angular momentum (orbital angular momentum, OAM) – it describes the direction of rotation and the strength of the twist of the photon and possesses high information capacity. Scientists have even compared the polarization of a photon in traditional quantum key distribution systems to a coin toss, and OAM to a dice with an infinite number of sides.


A photo – jesse ramirez – Unsplash

For data exchange, a scheme was proposed called “sending a parcel” (pass-the-parcel). A photon with encoded information in turn receives ten network participants, each of which performs certain operations with OAM without reading. Thus, the photon is not destroyed and returns to the sender. The latter makes a control reading and compares the state of the photon before and after transmission. Most importantly, the new approach allows you to distribute the key, even if only a part of the network participants trusts each other – for example, three or four. Classic systems cannot yet boast of such capabilities.

What’s up with the IT industry

Such developments bring the emergence of commercial and government quantum networks closer (such projects are already discuss at the US Department of Energy), reducing the cost of infrastructure and increasing its theoretical efficiency. So, in the Austrian Institute of Quantum Optics and Quantum Information convincedthat in the next five years, quantum networks will be able to unite computing devices at a distance of 50-100 kilometers.


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