Chip-to-chip entanglement distribution over 80-km multicore fiber link

Damien Roux; Giulia Guarda; Mujtaba Zahidy; Yunhong Ding; Siyan Zhou; Domenico Ribezzo; Battulga Munkhbat; Francesco Da Ros; Davide Bacco; Caterina Vigliar

arXiv · 2604.26791

Chip-to-chip entanglement distribution over 80-km multicore fiber link

Damien Roux·Giulia Guarda·Mujtaba Zahidy·Yunhong Ding·Siyan Zhou·Domenico Ribezzo·Battulga Munkhbat·Francesco Da Ros·Davide Bacco·Caterina Vigliar

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Abstract

Long-range quantum entanglement is essential for building large-scale quantum networks and unconditionally secure cryptographic systems based on quantum key distribution (QKD). While photonic integrated circuits offer a highly scalable platform, the fragility of phase coherence between spatial modes has prevented the distribution of path-encoded entanglement over long distances. Here, we report chip-to-chip distribution of path-encoded entangled states over 80 km between fully integrated silicon photonic transmitter and receiver chips. Telecom-band entangled photon pairs are generated via spontaneous four-wave mixing in on-chip spiral waveguides and distributed between chips over a dual-core, actively stabilized fiber link. Upon distribution, we measure a Bell state fidelity of $85.7 \pm 0.2 \%$. Implementing the BBM92 protocol with the same source, we obtain a secure key rate of 2.03 bit/s in the infinite-key regime. These results establish silicon photonic chips as a viable platform for long-distance path-encoded entanglement-based quantum key distribution, paving the way toward scalable, device-independent quantum networks.

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Damien Roux, Giulia Guarda, Mujtaba Zahidy, Yunhong Ding, Siyan Zhou, Domenico Ribezzo, Battulga Munkhbat, Francesco Da Ros, Davide Bacco, Caterina Vigliar. 2026-04-29. Chip-to-chip entanglement distribution over 80-km multicore fiber link. https://arxiv.org/abs/2604.26791

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