Qutech researchers successfully connected three quantum processors, forming the first multi-node quantum network. Such networks “will open up a range of novel applications, from unhackable communication and cloud computing with complete user privacy to high-precision time-keeping,” says Matteo Pompili, PhD student and a member of the research team. In addition, the scientists achieved a proof-of-principle demonstration of key quantum network protocols.
The rudimentary quantum network consists of three quantum nodes, at some distance within the same building. To make these nodes operate as a true network, the researchers had to invent a novel architecture that enables scaling beyond a single link. The middle node (called Bob) has a physical connection to both outer nodes (called Alice and Charlie), allowing entanglement links with each of these nodes to be established.
Bob is equipped with an additional quantum bit that can be used as memory, allowing a previously generated quantum link to be stored while a new link is being established. After establishing the quantum links Alice–Bob and Bob–Charlie, a set of quantum operations at Bob converts these links into a quantum link Alice-Charlie. Alternatively, by performing a different set of quantum operations at Bob, entanglement between all three nodes is established.
This first entanglement-based quantum network provides the researchers with a unique testbed for developing and testing quantum internet hardware, software and protocols. “The future quantum internet will consist of countless quantum devices and intermediate nodes,” says Ronald Hanson, who led the research team. “Colleagues at Qutech are already looking into future compatibility with existing data infrastructures.”
In due time, the current proof-of-principle approach will be tested outside the lab on existing telecom fiber – on Qutech’s Quantum Internet Demonstrator, of which the first metropolitan link is scheduled to be completed in 2022.