Deterministic delivery of remote entanglement on a quantum network

TL;DR

This paper demonstrates a method to reliably generate and deliver entangled quantum states between remote nodes at high rates, surpassing previous probabilistic approaches, crucial for scalable quantum networks.

Contribution

The authors develop a deterministic remote entanglement protocol using diamond spin qubits, achieving high entanglement rates and fidelity without pre- or post-selection, advancing quantum network capabilities.

Findings

Entanglement rate up to 39 Hz, three orders of magnitude higher than previous methods.

Remote entangled states with fidelity exceeding 0.5 at every 100 ms cycle.

Suppressed decoherence rate to 5 Hz using dynamical decoupling.

Abstract

Large-scale quantum networks promise to enable secure communication, distributed quantum computing, enhanced sensing and fundamental tests of quantum mechanics through the distribution of entanglement across nodes. Moving beyond current two-node networks requires the rate of entanglement generation between nodes to exceed their decoherence rates. Beyond this critical threshold, intrinsically probabilistic entangling protocols can be subsumed into a powerful building block that deterministically provides remote entangled links at pre-specified times. Here we surpass this threshold using diamond spin qubit nodes separated by 2 metres. We realise a fully heralded single-photon entanglement protocol that achieves entangling rates up to 39 Hz, three orders of magnitude higher than previously demonstrated two-photon protocols on this platform. At the same time, we suppress the decoherence rate of remote entangled states to 5 Hz by dynamical decoupling. By combining these results with efficient charge-state control and mitigation of spectral diffusion, we are able to deterministically deliver a fresh remote state with average entanglement fidelity exceeding 0.5 at every clock cycle of $\sim$100 ms without any pre- or post-selection. These results demonstrate a key building block for extended quantum networks and open the door to entanglement distribution across multiple remote nodes.