Researchers in the Netherlands have shown they can transmit quantum information via an intermediary node, a feature necessary to make the so-called quantum internet possible.
In recent years, scientists have argued that the quantum internet presents a more desirable network for transferring secure data, in addition to being necessary when connecting multiple quantum systems. All of this has been attracting investment from the US government, among others.
Despite the promise, there are still vital elements missing for the creation of a functional quantum internet.
Transferring quantum information — the superposition of states — between two network nodes becomes possible through the process of entanglement, which happens when scientists create two or more particles such that the quantum state of each particle cannot be described independently of the state of the others. In this way, researchers have shown they can “teleport” quantum information between two nodes.
Researchers at Qutech, a quantum computing research institute founded in 2014 by Delft University of Technology and the Netherlands Organization for Applied Scientific Research, have now demonstrated they can create the effect via an intermediary node, a necessary condition for a working computer network.
As a learning aid in the otherwise difficult to decipher field, PhD student Sophie Hermans and her colleagues named the network nodes with monikers relatable to the infoseccers among us: Alice, Bob and Charlie. Alice and Charlie have no direct connection between them.
The researchers’ demo first creates entangled quantum states between the neighboring nodes: Alice and Bob. The second node, or processor, then stores its entangled state. Next, Bob creates an entangled state with Charlie. The quantum scientists then exploited a peculiar effect known in their field. By measuring the state of Bob, they affect the entanglement, creating a direct connection between Alice and Charlie.
The team subsequently encoded the “message” information on an extra qubit, which when measured along with Charlie’s entangled state, teleports the information to Alice, according to a paper published in Nature this week.
While a significant demo of working concepts that may well become important in quantum networks, as with much in the quantum computing field, practical applications are some way off.
In an accompanying article, Oliver Slattery, doctor of physics at the Information Technology Laboratory, National Institute of Standards and Technology in Maryland and Yong-Su Kim, senior researcher at Center for Quantum Information, Korea Institute of Science and Technology, said constant teleportation of information around a quantum network remained some way off.
“Hermans et al [have] succeeded in teleporting quantum information between Alice and Charlie — two nodes without a direct connection. This achievement is not only a win for fundamental science but also represents an advance in the real-world problem solving required to move this fascinating quantum application to the next step.
“Reliable teleportation around a quantum network remains some way off, and this work makes clear the massive challenge ahead for the true realization of the quantum internet — but Hermans et al. offer a potential path forward. Increasing the robustness of the memories used to preserve entanglement will lead to even higher entanglement rates, and an improved optical interface will boost the efficiency with which remote nodes are entangled,” they said.
Three network nodes, Alice (A), Bob (B) and Charlie (C), are connected by means of optical fibre links (lines) in a line configuration. Each setup has a communication qubit (purple) that enables entanglement generation with its neighboring node
Nonetheless, the promise of moving quantum data around a network securely has such power the US government is determined not to be left out.
In 2020, the US Department of Energy laid out a “blueprint strategy” to develop a national quantum internet.
Secretary of Energy Dan Brouillette said: “By constructing this new and emerging technology, the United States continues with its commitment to maintain and expand our quantum capabilities.”
The US government statement at the time said the quantum internet “could become a secure communications network and have a profound impact on areas critical to science, industry, and national security.” ®