(SciTechDaily) Harvard and MIT researchers have found a way to correct for signal loss with a prototype quantum node that can catch, store and entangle bits of quantum information. The research is the missing link towards a practical quantum internet and a major step forward in the development of long-distance quantum networks.
Every form of communication technology— from the first telegraph to today’s fiber optic internet — has had to address the fact that signals degrade and are lost when transmitted over distances. The first repeaters, which receive and amplify signals to correct for this loss, were developed to amplify fading wire telegraph signals in the mid-1800s. Two hundred years later, repeaters are an integral part of our long-distance communications infrastructure.
Unlike classical repeaters, which amplify a signal through an existing network, quantum repeaters create a network of entangled particles through which a message can be transmitted. In essence, a quantum repeater is a small, special-purpose quantum computer. At each stage of such a network, quantum repeaters must be able to catch and process quantum bits of quantum information to correct errors and store them long enough for the rest of the network to be ready.
“This is the first system-level demonstration, combining major advances in nanofabrication, photonics and quantum control, that shows clear quantum advantage to communicating information using quantum repeater nodes. We look forward to starting to explore new, unique applications using these techniques,” said Mikhail Lukin, the George Vasmer Leverett Professor of Physics and a co-Director of Harvard Quantum Initiative.

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