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Deterministic delivery of remote entanglement on a quantum network
Peter C. Humphreys, Norbert Kalb, Jaco P. J. Morits, Raymond N. Schouten, Raymond F. L. Vermeulen, Daniel. J. Twitchen, Matthew Markham, Ronald Hanson
TL;DR
Extending quantum networks requires remote entanglement generation to outpace decoherence. This paper combines fully heralded single-photon entanglement with dynamical decoupling, demonstrating deterministic delivery at 0.56(1) fidelity.
Problem
Can a remote quantum link generate entanglement faster than its decoherence rate, reaching the threshold needed for deterministic delivery?
Source: p. 1Method
The paper combines a fully heralded single-photon entanglement protocol with dynamical decoupling to generate and protect remote entangled states.
Source: p. 2Results
0.56(1) fidelity demonstrated deterministic entanglement delivery, alongside 39 Hz entangling rates and a 5.0(3) Hz decoherence rate.
Source: pp. 4, 6Takeaways & Limitations
The demonstrated link efficiency beyond the critical threshold establishes this NV platform as a building block for extended quantum networks.
Source: pp. 2, 6At α = 0.05, residual photon distinguishability, double excitation, detector dark counts, and optical-phase uncertainty reduce fidelity by 3%, 4%, 3%, and 2%, respectively.
Source: p. 4
Abstract
from arXiv · showhide
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.