Light cages may advance the quantum internet

A team from Humboldt-Universität zu Berlin, the Leibniz Institute of Photonic Technology and the University of Stuttgart used 3D-nanoprinted hollow-core “light cages” filled with cesium vapor to make chip-scale quantum memories, and they demonstrated storage and retrieval of very weak light pulses containing a few photons for several hundred nanoseconds while integrating multiple identical memories on a single chip.

Researchers report a new chip-scale quantum memory that combines light and atomic vapor in 3D-nanoprinted hollow structures called "light cages," in a paper published in Light: Science & Applications. Storing quantum information is important for quantum computing and for long-distance quantum communication, where quantum repeaters depend on reliable memories. The devices are printed directly onto silicon chips using two-photon polymerization lithography and are designed for scalable integration. The team includes researchers from Humboldt-Universität zu Berlin, the Leibniz Institute of Photonic Technology, and the University of Stuttgart. Key facts: - Light cages are hollow-core waveguides that tightly guide light while allowing atoms to access the interior; cesium atoms diffuse into the light-cage cores in days rather than the months reported for conventional hollow-core fibers. - The structures are made with two-photon polymerization 3D-nanoprinting and printed directly on silicon chips for precise, reproducible fabrication. - Waveguides are coated to protect against chemical reaction with cesium; tests reported no signs of degradation after five years of operation. - The team stored very weak light pulses containing a few photons for several hundred nanoseconds and retrieved them using a control laser. - Multiple light-cage memories were integrated on a single chip inside a cesium vapor cell and produced nearly identical storage performance; reported fabrication variations were under 2 nanometers within a chip and under 15 nanometers between chips. - The platform operates slightly above room temperature and does not require cryogenic cooling or trapped-atom setups, and it offers higher bandwidth per memory mode compared with some alternatives. Summary: The light-cage approach provides a compact, reproducible way to combine guided light and atomic vapor on a chip, which the authors say could support quantum repeater networks and photonic quantum computing by synchronizing photons and providing controlled delays. The researchers report reproducible fabrication and near-room-temperature operation and state the method may be extendable to single-photon storage for longer times and to larger arrays of memories. Timelines for broader demonstrations or deployment were not given. Undetermined at this time.