Efficient reversible entanglement transfer between light and quantum memories

Reversible entanglement transfer between light and matter is a crucial requisite for the ongoing developments of quantum information technologies. Quantum networks and their envisioned applications, e.g., secure communications beyond direct transmission, distributed quantum computing, or enhanced sensing, rely on entanglement distribution between nodes. Although entanglement transfer has been demonstrated, a current roadblock is the limited efficiency of this process that can compromise the scalability of multi-step architectures. Herewe demonstrate the efficient transfer of heralded single-photon entanglement into and out of two quantum memories based on large ensembles of cold cesium atoms. We achieve an overall storage-and-retrieval efficiency of 85% together with a preserved suppression of the twophoton component of about 10% of the value for a coherent state. Our work constitutes an important capability that is needed toward large scale networks and increased functionality. (c) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement