Co-Propagation of Quantum Time Synchronization and Optical Frequency Transfer over a 122 km Hollow-Core Fiber

• URL: http://arxiv.org/abs/2602.19013v1
• Date: Sun, 22 Feb 2026 02:59:32 GMT
• Title: Co-Propagation of Quantum Time Synchronization and Optical Frequency Transfer over a 122 km Hollow-Core Fiber
• Authors: Huibo Hong, Xiao Xiang, Runai Quan, Rongduo Lu, Qian Zhou, Dawei Ge, Liuyan Han, Bo Liu, Ru Yuan, Dechao Zhang, Yuting Liu, Bingke Shi, ZhiGuang Xia, Xinghua Li, Mingtao Cao, Tao Liu, Ruifang Dong, Shougang Zhang,
• Abstract summary: Co-propagation of quantum and classical signals through shared optical fibers is crucial for scalable quantum networks.<n>Here, we overcome this long-standing challenge by leveraging the inherently ultralow nonlinearity of hollow-core fiber (HCF) to suppress SpRS noise.<n>We successfully demonstrate their simultaneous transmission over a 122-km link.
• Score: 14.5098510756184
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: The co-propagation of quantum and classical signals through shared optical fibers is crucial for scalable quantum networks. However, this coexistence is fundamentally limited by spontaneous Raman scattering (SpRS) from the bright classical light, which generates overwhelming noise that disrupts the single-photon-level quantum signals. Here, we overcome this long-standing challenge by leveraging the inherently ultralow nonlinearity of hollow-core fiber (HCF) to suppress SpRS noise. By operating both the quantum time synchronization (QTS) and classical optical frequency transfer (OFT) signals within the telecom C-band, separated by only ~10 nm, we successfully demonstrate their simultaneous transmission over a 122-km HCF link. With a classical OFT power of 1 mW, the QTS performance shows negligible degradation, maintaining sub-picosecond time stability at 2000 s, while the OFT achieves a fractional frequency instability of 10^-20. Near-sub-picosecond QTS stability is preserved even when the classical power is increased to 3 mW. Furthermore, simulations based on our experimental data indicate that with next-generation low-loss HCF, the platform can tolerate classical powers beyond 10 mW and extend the QTS range to over 500 km. By realizing a unified quantum-classical time-frequency distribution framework, this work establishes HCF as a highly capable and practical platform for future scalable quantum networks.

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