Entanglement of trapped-ion qubits separated by 230 meters

TL;DR

This paper demonstrates a quantum network linking two trapped-ion qubits over 230 meters using optical fibers, achieving high-fidelity entanglement and analyzing pathways for future improvements in long-distance quantum communication.

Contribution

It presents the first implementation of a 230-meter separated ion-based quantum network with entanglement generation and fidelity analysis, advancing scalable quantum communication.

Findings

Achieved up to 88.2% fidelity in ion entanglement

Successfully entangled ions separated by 230 meters

Identified routes to improve entanglement success probability

Abstract

We report on an elementary quantum network of two atomic ions separated by 230 m. The ions are trapped in different buildings and connected with 520(2) m of optical fiber. At each network node, the electronic state of an ion is entangled with the polarization state of a single cavity photon; subsequent to interference of the photons at a beamsplitter, photon detection heralds entanglement between the two ions. Fidelities of up to $(88.2+2.3-6.0)\%$ are achieved with respect to a maximally entangled Bell state, with a success probability of $4 \times 10^{-5}$. We analyze the routes to improve these metrics, paving the way for long-distance networks of entangled quantum processors.