It will perhaps be the first quantum technology to become a reality: the quantum internet. Researchers from QuTech in Delft have published in Science a detailed roadmap for the development of the quantum internet. They describe six phases, beginning with simple networks of qubits that already make a form of inherent secure quantum communication possible. In the final phase there are networks of quantum computers that are interconnected with quantum technology.

Communication technology

A quantum internet would be a revolution in communication technology, because it would use strange quantum phenomena such as entanglement. Researchers worldwide are working on the technology that would enable them to exchange quantum bits between any two points on Earth. Such quantum bits can have the values ‘1’ and ‘0’ as in classical bits, but also both at the same time. And they can be ‘entangled’: their states are then connected, so that the measurement of one has an immediate effect on the other.

Coordination

As a consequence the quantum internet has unique properties that will always be out of reach for the classical internet. The first as that through entanglement, activities in two widely separated places can be very accurately coordinated. This allows clocks to be synchronised very accurately and observations from telescopes can be virtually connected so that astronomers obtain much sharper images. The second property is that quantum connections are inherently secure. When two qubits are completely entangled, then it is fundamentally impossible to eavesdrop on the connection. This makes entanglement eminently suitable for applications that require security and privacy.

Prepare and measure

At the first phase of an actual quantum network – a ‘prepare and measure network’ – it is possible to send quantum bits between any to points in a network. This is already sufficient to support various cryptographic applications. The most advanced phase the the quantum interconnection of fully operational quantum computers.

The expectation is that the first quantum networks for sending end-to-end qubits will be realised in the next few years, on the way to large-scale quantum networks.