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. Here we 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.
The spatial modes of light, carrying a quantized amount of orbital angular momentum (OAM), is one of the excellent candidates that provides access to high-dimensional quantum states, which essentially makes it promising towards building high-dimensional quantum networks. Quantum memory with efficiency above 50% is an essential condition for beating the no-cloning limit or in the one-way quantum computation. However, up till now, the highest storage efficiencies achieved for OAM states are below 30%, which is an obstacle towards practical applications. In this paper, we report the storage and retrieval of photonic qubits encoded with OAM state in an elongated cold rubidium atomic ensemble, achieving a storage efficiency around 65% with an average conditional fidelity above 98%. Our work constitutes an efficient node that is needed towards high dimensional and large scale quantum networks.
Highly-efficient entanglement storage in quantum memories is a critical requirement for quantum networks. We present an experiment where we stored single-photon entanglement into two atomic-ensemble based quantum memories with an overall efficiency of 87%.
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