Soon, we may be living in quantum cities. A computer simulation of a聽city where universities, data centres and telecommunication hubs are connected by quantum internet聽suggests that existing technology is close to making it a reality.
In a quantum city, telecommunications and institutions that deal with vast quantities of data would be connected in a network that uses quantum devices instead of modems and routers. These devices would take advantage of quantum effects to make information sharing within the network exceptionally secure. Similar networks already exist, but they tend to be small, slow or limited in application.
at Sorbonne University in France and her colleagues used a computer simulation to assess whether existing technology, such as optical fibres and devices that generate light encoded with quantum information, could turn Paris into a functional quantum city.
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They simulated a network made of a hub called the Qonnector surrounded by users, or Qlients, connected to it by conventional optical fibres. The Qlient closest to the hub was 1 metre away while the most distant one was 31 kilometres removed, farther away than the city of Paris is wide.
The Qonnector could encode information into light signals with special quantum properties, then transmit them to Qlients. For instance, it could quantumly entangle, or connect, particles of light within the fibre, so that if one particle is tampered with by a hacker, its entangled partners always automatically change, revealing the hacking.
The team used this set-up to simulate multiple processes for how the Qonnector may share quantum-encrypted information with one Qlient at a time or with many at once. In all simulations, the researchers chose network specifications, including how many signals can be transmitted through fibres at once and how often. They also simulated how Qlients could use the quantum internet to remotely operate a powerful quantum computer if one was added into the network. Some quantum computers can currently be accessed and programmed remotely through the cloud, but not yet through fibres.
Quantum signals that guarantee secure communication can be easily disturbed by their environment. In fact, they can lose their special quantum properties or become unintelligible noise when they travel through long fibres or fibres exposed to heat or vibrations. But Diamanti says that simulating a realistic quantum Paris showed that these challenges do not render existing sources of quantum signals and communications useless in all cases. Simulations mostly returned encouraging results, she says.
Communication with the Qlients farthest away and attempts to share long, encrypted codes with more than three Qlients had impractically high error rates. But some procedures for sharing complex, encrypted information between a Qonnector and a single Qlient and for operating remote quantum computers worked well. These experienced very few glitches in the network.
鈥淭he concept of metropolitan quantum networks is gaining a lot of attention these days and these simulations show the necessary tech is not unreasonably futuristic,鈥� says at the quantum communication start-up Qunnect in New York.
at Delft University of Technology in the Netherlands says that says that these simulations offer a timestamp for where quantum communication technology is now, but also hint that future upgrades will be needed. Turning cities larger than Paris into quantum cities or implementing the most advanced, secure communications methods for thousands of users will require developing new devices like quantum memories for storing information, and quantum repeaters for amplifying weak signals, he says.
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