Mapping photonic entanglement into and out of a quantum memory

TL;DR

This paper presents a protocol for mapping photonic entanglement into atomic ensembles and retrieving it, enhancing quantum network capabilities by enabling on-demand entanglement with improved efficiency.

Contribution

The authors introduce a coherent mapping protocol that separates entanglement generation from storage, improving upon probabilistic methods for quantum networking.

Findings

Achieved 17% efficiency in mapping entanglement back to photonic modes.

Separated entanglement creation and storage for better control.

Demonstrated potential for on-demand entanglement in quantum networks.

Abstract

Recent developments of quantum information science critically rely on entanglement, an intriguing aspect of quantum mechanics where parts of a composite system can exhibit correlations stronger than any classical counterpart. In particular, scalable quantum networks require capabilities to create, store, and distribute entanglement among distant matter nodes via photonic channels. Atomic ensembles can play the role of such nodes. So far, in the photon counting regime, heralded entanglement between atomic ensembles has been successfully demonstrated via probabilistic protocols. However, an inherent drawback of this approach is the compromise between the amount of entanglement and its preparation probability, leading intrinsically to low count rate for high entanglement. Here we report a protocol where entanglement between two atomic ensembles is created by coherent mapping of an entangled state of light. By splitting a single-photon and subsequent state transfer, we separate the generation of entanglement and its storage. After a programmable delay, the stored entanglement is mapped back into photonic modes with overall efficiency of 17 %. Improvements of single-photon sources together with our protocol will enable "on demand" entanglement of atomic ensembles, a powerful resource for quantum networking.