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Laser‑written Glass Chip Pushes Quantum Communication Toward Practical Deployment

Researchers at the University of Padua and partners have fabricated a high‑performance quantum coherent receiver directly inside borosilicate glass using femtosecond laser writing. The glass chip delivers ultra‑low insertion loss (~1 dB), polarization‑independent operation, and a 73 dB common‑mode rejection ratio, outperforming many silicon‑based receivers. It simultaneously demonstrated a record‑high 42.7 Gbit/s secure random‑bit generation and a 3.2 Mbit/s secret‑key rate over a 9.3 km fiber link using continuous‑variable QKD. The approach promises scalable, low‑cost photonic integration compatible with existing telecom infrastructure.