Entangling Two Rydberg Superatoms via Heralded Storage

Heralded storage of photons is crucial for advancing quantum networks. Previous realizations have primarily relied on single atoms strongly coupled to optical cavities. In this work, we present the experimental realization of heralded storage using a Rydberg superatom, a mesoscopic atomic ensemble operating in the strong blockade regime. In our approach, an input photon is initially stored in the superatom via electromagnetically induced transparency. Subsequently, a second photon is emitted conditioned on the success of the first photon's storage. Because of the collectively enhanced interaction, both the storage and the emission of the herald photon can be rather efficient in principle. As a demonstration of this technique, we use it to entangle two remote Rydberg superatoms. This method obviates the need for an intermediate node, which is commonly employed in traditional interference-based remote entanglement schemes. Our results showcase the potential of performing cavity-QED-like experiments with Rydberg superatoms. This work opens pathways for numerous applications in quantum networks and linear optical quantum computing.