# Semi-Deterministic Entanglement between a Single Photon and an Atomic Ensemble

## TL;DR

This paper demonstrates a high-efficiency scheme for entangling a single photon with an atomic ensemble using Rydberg blockade, achieving 50% efficiency and high fidelity, advancing quantum network capabilities.

## Contribution

The authors propose and experimentally realize a novel scheme for atom-photon entanglement with 50% efficiency using Rydberg blockade and momentum encoding.

## Key findings

- Achieved 50% entanglement creation efficiency.
- Measured fidelity of 0.901 for atom-photon entanglement.
- Verified the single-photon nature of retrieved optical fields.

## Abstract

Entanglement between a single photon and a matter qubit is an indispensable resource for quantum repeater and quantum networks. With atomic ensembles, the entanglement creation probability is typically very low to inhibit high-order events. In this paper, we propose and experimentally realize a scheme which creates atom-photon entanglement with an intrinsic efficiency of 50%. We make use of Rydberg blockade to generate two collective excitations, lying in separate internal states. By introducing the momentum degree of freedom for the excitations, and interfering them via Raman coupling, we entangle the two excitations. Via retrieving one excitation, we create the entanglement between the polarization of a single photon and the momentum of the remaining atomic excitation, with a measured fidelity of 0.901(8). The retrieved optical field is verified to be genuine single photons. The realized entanglement may be employed to create entanglement between two distant nodes in a fully heralded way and with a much higher efficiency.