High-rate, high-fidelity entanglement of qubits across an elementary quantum network

TL;DR

This paper reports the successful demonstration of high-rate, high-fidelity entanglement between trapped-ion qubits across a quantum network using a novel fiber-optic setup, achieving near-local operation quality.

Contribution

It introduces a new geometry for efficient photon collection that maintains high fidelity in remote ion-photon entanglement, enabling fast and reliable quantum networking.

Findings

Remote Bell pairs with fidelity 0.940 achieved

Entanglement rate of 182 pairs per second

High-efficiency photon collection method demonstrated

Abstract

We demonstrate remote entanglement of trapped-ion qubits via a quantum-optical fiber link with fidelity and rate approaching those of local operations. Two ${}^{88}$Sr${}^{+}$ qubits are entangled via the polarization degree of freedom of two photons which are coupled by high-numerical-aperture lenses into single-mode optical fibers and interfere on a beamsplitter. A novel geometry allows high-efficiency photon collection while maintaining unit fidelity for ion-photon entanglement. We generate remote Bell pairs with fidelity $F=0.940(5)$ at an average rate $182\,\mathrm{s}^{-1}$ (success probability $2.18\times10^{-4}$).