Silicon chip-based polarization entanglement distribution through ultra-low-loss fiber: splicing and polarization control

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.