Remote Quantum Networking with Single Rare-earth Ions: Tripartite Entanglement Heralding

Remote entanglement distribution in quantum networks has applications in connecting quantum computers and secure information transfer. While bipartite entanglement has been shown in multiple systems, tripartite entanglement distribution has only been shown with limited platforms, highlighting the need for more scalable platforms and protocols.

Here, we demonstrate the scalability of a novel entanglement protocol (presented in the previous talk) by generating tripartite entangled states of ¹⁷¹Yb:YVO₄ optically addressed qubits, distributed between two remote nanophotonic cavities.

Specifically, we show that entanglement of three ¹⁷¹Yb ions can be heralded with a single photon protocol. Since the ions possess different optical frequencies, the stochastic photon detection time imprints two random quantum phases, leading to a mixed state. However, with precise measurement of the photon arrival time, the phases can be evaluated and counteracted in real-time via a feedforward phase shift of the qubits. Through this real-time phase compensation, we are able to prepare entangled three-ion W states with a fidelity of 60% and a heralding rate of 3 Hz. This result shows both the scalability of our platform and the robustness of our entanglement protocol.