Curator's Take
AI Commentary
This article demonstrates that continuous‑variable QKD can run at ≈150 Mb/s alongside a 7‑Tb/s classical data stream on the same hollow‑core fiber—a scale previously unattainable in standard silica fibers because of excess noise from the weak quantum signals. By leveraging ultra‑low‑loss anti‑resonant guidance and carrier‑assisted phase recovery, the authors push the coexistence distance to a 24 km link (projected to 100 km equivalent) while tolerating classical launch powers up to 15 dBm without any bandpass filtering. The result shows a realistic pathway for quantum‑secured links to be deployed within existing high‑capacity optical networks, though scaling to longer spans will still require careful management of fiber nonlinearity and finite‑size security margins.
— Mark Eatherly
Summary
Quantum key distribution (QKD) can provide secret keys with security rooted in quantum mechanics, but operation alongside high-capacity classical traffic remains limited by the excess-noise budget of weak quantum states in conventional solid-core fiber. Here, we combine ultralow-loss anti-resonant hollow-core fiber with residual-carrier-assisted discrete-modulation continuous-variable QKD (DM-CV-QKD) to address both propagation-induced coexistence noise and low-SNR phase recovery. Over a 24.3-km hollow-core link with 3.3-dB end-to-end loss, a dual-polarization 15-Gbaud DM-CV-QKD channel achieves an average asymptotic secret-key rate (SKR) of 153.22 Mb/s and a finite-size SKR of 149.99 Mb/s, while 39 coherent wavelength-division-multiplexed channels deliver an aggregate data rate of 7.6 Tb/s and a net data rate of 7.2 Tb/s. The system can even sustain a positive SKR under a high classical launch power of up to 15 dBm, without an optical bandpass filter (BPF). Finite-size analysis against collective attacks further yields a projected positive secret-key rate at a 100-km-equivalent condition. These results show that an anti-resonant hollow-core fiber, combined with carrier-assisted phase recovery, can greatly extend the operating regime of shared-fiber quantum-secured coherent links, pointing to a promising approach for integrating high-rate CV-QKD with high-capacity optical networks.