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Quantum 2.0 Conference and Exhibition

Entanglement Distribution over Ultra-Low-Loss Fiber with a Silicon Chip Source

Jinyi Du, Xingjian Zhang, En Teng Lim, George F. R. Chen, Hongwei Gao, Dawn T. H. Tan, Alexander Ling

Published Jan 1, 2025• 0 citations
Publisher

Abstract

We develop and demonstrate a silicon chip generating 460,000 entangled photon pairs per second with 97.90(3)% fidelity. The photons were transmitted over 155 km of deployed fiber (66 dB loss) and ultra-low-loss fiber spools (0.16 dB/km), achieving extended transmission distances.
DOI
10.1364/quantum.2025.qm3a.6

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Entanglement distribution is critical for quantum networks, enabling secure communication and distributed quantum computing. We demonstrate long-distance polarization-entangled photon pair distribution using a silicon nanophotonic chip and ultra-low-loss (ULL) fiber. The polarization-entangled photons from the silicon chip achieve a fidelity of 97.90% with a raw observed entangled photon rate of 460,000 pairs/s. The chip is efficiently coupled to optical fiber with losses as low as 0.64dB per facet. Leveraging ULL fiber (0.16dB/km), we extend the entanglement distribution distance to over 300km, surpassing the previous record of 155km using deployed fiber. Key advancements include optimized splicing (sub-0.01dB loss) and active polarization correction, ensuring stable entanglement over long distances. This work highlights the potential of silicon photonics and ULL fiber for scalable and practical quantum communication networks.
Transmitting entangled states over long distances is crucial for developing quantum networks. Previous demonstrations using satellites or fibers relied on photon pairs generated from bulk crystal arrangements. Polarization entanglement distribution based on complementary metal-oxide-semiconductor (CMOS)-compatible silicon chips has long been restricted to lab-scale demonstrations spanning only a few meters due to the difficulty of achieving sufficient off-chip brightness. Here, we report a silicon chip platform that provides an off-chip entangled photon pair brightness ranging from 8,000 to 460,000 pairs per second, exceeding previous reports by 3 orders of magnitude. The entanglement fidelity reaches 99.85(6)% and 97.90(3)%, respectively. After addressing key challenges in long-distance entanglement distribution over deployed fiber, including phase drift and chromatic dispersion, entangled photons were successfully distributed over 155 km (66 dB loss). These results demonstrate that CMOS-compatible silicon chips can perform competitively with bulk crystal sources and represent an important step toward scalable, chip-based quantum networks.
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