A peek at the quantum internet: secrets and superpositions

Nature speculates about the ways quantum computing will change the way the internet works, with unbreakable privacy and more:

The first stages promise virtually unbreakable privacy and security in communications; a more mature network could include a range of applications for science and beyond that aren’t possible with classical systems, including quantum sensors that can detect gravitational waves.

A prominent team of quantum-internet researchers at Delft University of Technology in the Netherlands has now released a roadmap laying out the stages of network sophistication — and detailing the technological challenges that each tier would involve.

Quantum networks and quantum computing share many concepts and techniques. Both take advantage of phenomena that have no analogue in classical physics: for example, a quantum particle such as an electron or a photon can be in one of two well-defined states of spinning, clockwise or anticlockwise — but also in a simultaneous combination of both, called a superposition. And two particles can be ‘entangled’, in which they share a common quantum state. This makes them act in seemingly coordinated ways (such as spinning in opposite directions) even when they are separated by vast distances.

In stage 1, users will start getting into the quantum game, in which a sender creates quantum states, typically for photons. These would be sent to a receiver, either along an optical fibre or through a laser pulse beamed across open space. At this stage, any two users will be able to create a private encryption key that only they know.

The technology will also enable users to submit a quantum password, for example, to a machine such as an ATM. The machine will be able to verify the password without knowing what it is or being able to steal it.

Stage 1 has not been tried on a large scale, but it is already technologically feasible at the scale of small cities, Wehner says….

But there could be applications outside of science, too. In an election, a stage-5 quantum internet could allow voters to select not just one candidate, but a ‘superposition’ of candidates, which includes, say, their second-favourite option. “Quantum voters,” says physicist Nicole Yunger Halpern at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, could use “strategic-voting schemes that classical voters can’t implement”. And quantum techniques might help large groups to coordinate and reach a consensus, for example, to validate electronic currencies such as Bitcoin.