# High Purity Single Photons Entangled with an Atomic Memory

## TL;DR

This paper demonstrates a highly pure single-photon source from a trapped barium ion, optimized for quantum networking, achieving exceptional photon purity and improved entanglement fidelity.

## Contribution

The work introduces a novel single-photon source with unprecedented purity from a trapped ion, enhancing quantum network node performance.

## Key findings

- Single-photon purity of g^{2}(0)=(8.1±2.3)×10^{-5} achieved
- Optimized tradeoff between photon rate and entanglement fidelity
- Tailored spatial mode improves polarization qubit collection

## Abstract

Trapped atomic ions are an ideal candidate for quantum network nodes, with long-lived identical qubit memories that can be locally entangled through their Coulomb interaction and remotely entangled through photonic channels. The integrity of this photonic interface is generally reliant on purity of single photons produced by the quantum memory. Here we demonstrate a single-photon source for quantum networking based on a trapped $^{138}\mbox{Ba}^+$ ion with a single photon purity of $ g^{2}(0)=(8.1\pm2.3)\times 10^{-5} $ without background subtraction. We further optimize the tradeoff between the photonic generation rate and the memory-photon entanglement fidelity for the case of polarization photonic qubits by tailoring the spatial mode of the collected light.