Technology
The potential of quantum computers is astounding, with the ability to solve complex problems that not even the most powerful supercomputer could. We are not there yet, despite some positive steps forward. Quantum computers will also benefit from a quantum communication network – a quantum internet. Now, researchers have been able to test a quantum network using existing infrastructure.
The system, developed by Toshiba Europe, spanned 254 kilometers (158 miles) between the German cities of Frankfurt and Kehl, with a connecting third station in Kirchfeld. It used existing fibers, and the whole system was at room temperature, showcasing a method that doesn’t require cooling down the infrastructure to near absolute zero.
According to the team, this is a new record distance for real-world and practical quantum key distribution.
It might seem peculiar to be excited by the fact that the same internet you are using to read this can also accommodate special photons from a quantum communication network, but the simple truth is that those photons are created in a quantum state so that they are entangled or in superposition. Thanks to these quantum properties, these communications cannot be decrypted. The drawback is that the states are fragile.
Just a few months ago, Professor Prem Kumar and his team at Northwestern University demonstrated that it is possible to send such a fragile state over a noisy internet cable by choosing the right wavelength. The entangled photons were at 1,290 nanometers and traveled through a 30.2-kilometer (18.8-mile) optical fiber, which simultaneously carried 400 Gbps internet traffic in the widely used C-band transmission light (1,547 nanometers).
“We found we could perform quantum communication without interference from the classical channels that are simultaneously present,” Kumar said in a statement at the time. Kumar expanded on this work and explained how it is connected to teleportation (and why we can’t teleport humans) in a feature for our magazine CURIOUS.
The Toshiba Europe approach is a significant improvement on previous approaches. While the longest distances are made possible using satellites, employing real infrastructure shows that a quantum internet doesn’t need a whole new system of cables and more to work.
Beyond un-hackable messages, a quantum internet could be used to connect quantum computers together to solve even more complex problems. It could also be used to keep the system in sync with exquisite precision. Quantum computers and the quantum internet won’t be the everyday tech of tomorrow, but these tests are crucial to make sure that these technologies can become commonplace.
The study is published in the journal Nature.
