Multipartite Mixed-Species Entanglement over a Quantum Network

TL;DR

This paper demonstrates the creation and storage of multipartite entangled states across a quantum network using trapped-ion qubits of different species, with entanglement extended over macroscopic distances and stored for seconds.

Contribution

It introduces a method for generating and extending multipartite mixed-species entanglement over a quantum network with long storage times.

Findings

Successfully created multipartite entangled states of up to four qubits.

Extended entanglement over macroscopic distances via optical fibre links.

Achieved storage of entangled memory qubits for approximately 10 seconds.

Abstract

We generate multipartite entangled states of two, three and four matter qubits, where the entanglement is distributed over macroscopic distances via a photonic network link. Trapped-ion ${}^{88}\text{Sr}^+$ qubits are entangled directly via the optical fibre link, and the entanglement is subsequently extended to ${}^{43}\text{Ca}^+$ memory qubits co-trapped in each network node, using local mixed-species logic gates. We create remotely entangled $\text{Sr}^+$-$\text{Ca}^+$ and $\text{Ca}^+$-$\text{Ca}^+$ states, as well as mixed-species Greenberger-Horne-Zeilinger (GHZ) states of up to four qubits. We demonstrate storage of the remotely-entangled memory qubits for $\sim10~\text{s}$, more than $100\times$ the creation time.