Automated distribution of high-rate, high-fidelity polarization entangled photons using deployed metropolitan fibers

Distributing high-fidelity, high-rate entanglement over telecommunication infrastructure is one of the main paths towards large-scale quantum networks, enabling applications such as quantum encryption and network protection, blind quantum computing, distributed quantum computing, and distributed quantum sensing. However, the fragile nature of entangled photons operating in real-world fiber infrastructure has historically limited continuous operation of such networks. Here, we present a fully automated system capable of distributing polarization entangled photons over a 34 km deployed fiber in New York City. We achieve end-to-end pair rates of nearly 510⁵ pairs/s and entanglement fidelity of approximately 99\%. Separately, we achieve 15 days of continuous distribution, with a network up-time of 99. 84\%. Our work paves the way for practical deployment of 24/7 entanglement-based networks with rates and fidelity adequate for many current and future use-cases.