Researchers from QuTech, a collaboration between TU Delft and TNO, have a first with the teleport of quantum information between two nodes that did not have a direct connection with each other. According to QuTech, this teleportation could eventually form the ‘backbone’ of a super-secure quantum internet.
“We showed that we can bring everything together, to make it all work at once. Because you are, as it were, dealing with matters that have conflicting interests. It is a blueprint of what will become possible,” says Hans Beukers, one of the scientists who participated in the study.
Quantum computers calculate with quantum physics, the theory about the world on the smallest scale. Unlike bits in regular computers, quantum bits (qubits) can be not only 0 or 1, but also 0 and 1 at the same time. This allows quantum computers to make calculations that are not possible with current supercomputers. Quantum computers can therefore contribute to all kinds of important research, such as new materials that can trigger an energy revolution or medicines that are tailored to the individual.
Connecting quantum computers requires a different kind of internet, which uses an ‘entanglement’ between qubits. What you do with one qubit has a direct influence on the other, even if those qubits are very far apart.
The Delft researchers ‘entangled’ three qubits to create a quantum network. Until now, that was only possible between two points.
From Alice to Charlie
Alice, Bob and Charlie are what the researchers call the three nodes. They used the entanglement to teleport information from Alice to Charlie, skipping the intermediate Bob.
Alice and Bob were connected by fiber, Bob and Charlie, but Alice and Charlie had no physical connection. Bob enabled the teleportation of information between Alice and Charlie by reconciling two entanglements.
When measuring quantum states, the information is immediately lost. This also happens with a measurement at Charlie, but that information immediately appears on Alice’s side. The qubit is transferred encrypted, with Charlie’s measurement result determining the key. Alice then performs the quantum operation needed to decode the qubit.
One of the great promises of a quantum internet is communications that cannot be intercepted or tapped. If someone tried that, the information would disappear instantly. Only the sender and recipient have access to certain information.
“With today’s computers and the Internet, anything can be cracked, as long as you have a computer that is powerful enough. Mathematical security can be broken, physics cannot. It is inherently safe, it is unbreakable,” says Beukers. “With quantum internet, it is immediately noticed if someone is fiddling with certain information.”
He gives the example of a government agency that sends nuclear secrets to another government organization. “It may not be possible to crack a message like this now, but you want it to still be the case 30 years from now. That is the promise of quantum internet.”
In addition to secure communication, quantum internet can also offer more privacy, says Beukers. “Services then no longer need all kinds of information about you in order to recognize and help you.”
There is still a lot of work to be done before quantum computers start working together in an international network. “First we need to take the technology out of the lab and make it more robust in the field.” According to the researchers, this was almost the maximum achievable with the design used. “To make it scalable, a different set-up is needed. We’re looking for other particles to create entanglements with. Experiments are underway, but it is still in its infancy.”
Research is also being conducted into the use of infrared light to enable quantum internet via normal fiber optic cables. “We will probably be ten years later before there is a global network of quantum computers.”