We all want secure communication. But how secure do we want it to be? Over the decades, we have made this choice time and time again. We want things to be as secure as possible provided that they remain convenient and affordable. Quantum communication is widely seen as the best possible security however, it is intrinsically a point to point two party protocol. Which makes quantum communication between many users inconvenient and expensive. In today’s networked world, quantum networks are a hot research topic.

Researchers in the group of Rupert Ursin at IQOQI Vienna have figured out a fundamentally different way of interconnecting users and distributing entanglement – a basic resource used for quantum communication. Their novel network architecture allows them to seamlessly connect several users to the same network while allowing simultaneous communication between all users. Better yet, the technology is entirely passive which means that there are no complex steps required to route the entanglement to different users. This means few failures and a cheaper and more reliable quantum network.

In the paper 'An entanglement-based wavelength-multiplexed quantum communication network ' just published in Nature, the researchers show that many users can connect to a single source of entanglement with very basic and simple modules each. Further, the wavelength based distribution scheme used allows users to be added and removed from the network without affecting the software or hardware of other users. Currently, the researchers have shown a 4 user fully connected network which they argue can easily support more connections. However, there is a limit. When asked if the limit is fundamental, Siddarth Joshi – an author of the paper replied: “The number if users is limited by available wavelength channels and the desired fully connected network topology. However, we are working on a new scheme that will allow even more users to connect to the network.” Other research into quantum networks is underway funded by the European flagship and by many scientists from all over the world.