Physicists at the Kastler Brossel Laboratory in Paris have reached a milestone in the combination of cold atoms and nanophotonics. Using fiber-addressable atoms, they have created the first wired atomic entangled state that can be stored and later read out as a guided single photon.
The integration of cold atoms with nanoscopic waveguides has raised a lot of interest in recent years, giving birth to a booming research field known as waveguide quantum electrodynamics. Such integrated platforms hold the promises of better scalability and figures of merit than free-space implementations, which will eventually lead to on-chip technologies for a future quantum internet. This combination could be a new frontier for atom-photon physics. So far, the experimental progress has been limited due to the very challenging combination of these two worlds.
In the journal Nature, Professor Julien Laurat and his colleagues at Sorbonne University report that they have used an atomic register composed of a chain of individual cesium atoms tightly trapped along a nanoscale waveguide. In this configuration, they were able to generate and store a single atomic excitation, as in a quantum memory, and subsequently read it out in the form of a guided single photon.