With the promise to control the physical world in ever smaller scales, quantum systems are coming into the center stage of modern technology. A forerunner in this quest is the science of quantum information. Diverse few-qubit systems have been implemented, and photonic quantum communication has been demonstrated for up to 150 km. However, scalability remains a grand challenge. One solution leading to scalable quantum technology is the quantum networks.
A quantum network consists of matter nodes to store and process quantum information, optical channels to transport quantum information, and critically, matter-light quantum interfaces between the nodes and the channels that enable efficient distribution of quantum information across the network. Using atomic ensembles as matter nodes, we establish efficient quantum interfaces between atoms and photons based on collective matter-light interactions, and demonstrate the essential capabilities of quantum networks -- generation, storage and distribution of entanglement between remote quantum nodes.