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.
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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.
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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.