Researchers at QuTech, a collaboration between TU Delft and TNO, have pioneered the teleportation of quantum information between two nodes that had no direct connection to each other. According to QuTech, this teleportation could form the ‘backbone’ of a super-secure quantum internet in the long term.
“We’ve shown that we can bring everything together to make it all work at the same time. Because you’re dealing with things that kind of have conflicting interests. It’s a blueprint of what’s going to be possible,” says Hans Beuker. one of the scientists who participated in the study.
Quantum computers rely on quantum physics, the theory of the world at the smallest scale. Unlike bits in ordinary computers, quantum bits (qubits) can be not only 0 or 1, but also 0 and 1 at the same time. As a result, quantum computers can do calculations that are not possible with current supercomputers. Quantum computers can therefore contribute to all kinds of important research, such as new materials that could lead to an energy revolution or personalized medicine.
Connecting quantum computers requires a different kind of internet, which uses an ‘entanglement’ between qubits. What you do with one qubit immediately affects the others, even if these qubits are very far apart.
The Delft researchers ‘filtered’ three qubits to create a quantum network. Until now, this has only been possible between two points.
From Alice to Charlie
Alice, Bob and Charlie the researchers call the three nodes. They used the entanglement to teleport information from Alice to Charlie while skipping the intervening Bob.
Alice and Bob were connected via fiber optics, Bob and Charlie too, but Alice and Charlie had no physical connection. Bob enabled the teleportation of information between Alice and Charlie by joining two entanglements.
When measuring quantum states, the information is immediately lost. This also happens with a measurement at Charlie’s, but that information then appears directly on Alice’s page. The qubit is transmitted encrypted, with Charlie’s measurement result determining the key. Alice then performs the necessary quantum operation to decrypt the qubit.
Not to break
One of the great promises of a quantum internet is communications that cannot be intercepted or eavesdropped. If someone tried to do that, the information would instantly disappear. Only the sender and recipient can then access certain information.
“With today’s computers and the Internet, everything can be hacked if you only have a computer that is powerful enough. Mathematical security can be broken, physics cannot. It is inherently safe, it is unbreakable,” says Beukers. “With the quantum internet, if someone messes with certain information, it will be immediately noticed.”
He gives the example of a government agency sending nuclear secrets to another government organization. “Such a message may not be broken now, but you want it to still be the case in 30 years. That is the promise of the quantum internet.”
In addition to secure communication, the quantum internet could also offer more privacy, says Beukers. “Services then no longer need all kinds of information about you to be able to recognize you and help you.”
There is still a lot of work to be done before quantum computers can work together in an international network. “First we need to take the technology out of the lab and make it more robust in practice.” According to the researchers, this was almost the maximum achievable with the set-up used. “To make it scalable, a different set-up is needed. We’re looking for other particles to make entanglements with. There are experiments going on with this, but it’s still in its infancy.”
Research is also underway into using infrared light to make the quantum internet possible via normal fiber optic cables. “Before there is a worldwide network of quantum computers, we will probably be ten years longer.”