Quantum Internet can generate a secure encryption key.

Quantum communication systems are more secure than regular networks as they are dependent on the quantum properties of photons instead of easily crackable computer code. Building a quantum communication, however, is expensive. "It just doesn't scale well," states Siddarth Joshi at the University of Bristol, UK.

Mr Joshi and his colleagues have built a kind of quantum network applying a method called multiplexing entanglement. It is a quantum property that sees two objects like a pair of photons linked in a way that measuring one of them influences the measured state of the other regardless of their distance. It can be used to create a secure encryption key.

As connecting users one-to-one is costly when dealing with an extensive network, multiplexing entanglement splits photons from a single laser as per their wavelength. Each wavelength has a capacity of holding data stream. It means the system could support between 50 and 100 users with existing hardware, adds Mr Joshi.

The team examined the system with eight users on existing optical fibres in Bristol. Over 100 people can potentially use the system because not everyone requires to be connected all the time.

The team claims its test system is the world's largest entanglement-based network, in terms of numbers of users. And it is different from more extensive networks like One in China, that uses a technique called ‘trusted nodes’. A message is included along a line of users, means any legitimate user on the network can listen in.

Siddarth Joshi says, "The Chinese network is addressing how to build a 2000-kilometre link between Beijing and Shanghai. We are advocating how to connect everyone together."

Harun Siljak at Trinity College Dublin, Ireland says, "The step away from trusted nodes is a significant development, but the Bristol development is an essential step towards the quantum internet idea of unprecedented security and privacy."

Siljak cautions, "This is a proof of concept and has queries about keeping the error rate of photon recognition in realistic bounds when operating a more extensive network. If error rates exceed a certain percentage, it may not generate secure encryption keys."

However, Joshi believes, "risk is manageable, and the method can be used to connect millions of devices." In short, they are trying to build the quantum internet.