Abstract：A Chinese research team has achieved key breakthroughs in advanced photonic systems, including 16‑dimensional QKD over 50 km of few‑mode fiber with 1.2% bit error rate, and 11 wavelength pairs generated within a 35.2 nm bandwidth on an AlGaAs‑on‑insulator platform. The team also verified high‑fidelity energy‑time entanglement with a CHSH Bell inequality violation exceeding 12 standard deviations.

A Chinese research team led by Zheng Xiaodong, Xu Jing, and Liu Chenbo from the State Key Laboratory of Solid-State Microwave Devices and Circuits, in collaboration with Xia Lina from Nanjing Normal University, has achieved notable progress in advanced photonic systems, covering high‑dimensional quantum key distribution, on‑chip multi‑wavelength sources, and energy‑time entanglement.

Using few‑mode fiber quantum frequency coding, the team demonstrated 16‑dimensional quantum key distribution over a 50‑km link with a quantum bit error rate of only 1.2%, outperforming most existing discrete‑variable systems. They also developed a mode demultiplexer with crosstalk below –20 dB, supporting high‑fidelity high‑dimensional quantum states.

On the AlGaAs‑on‑insulator platform, the team generated 11 independent wavelength pairs within a 35.2 nm bandwidth (free spectral range ~200 GHz) — the first such high‑performance on‑chip multi‑wavelength source on this platform. It achieves an average spectral brightness of 2.64 GHz·mW⁻²·nm⁻¹ and a coincidence‑to‑accidental ratio exceeding 118 across the spectrum.

Using Franson interferometry, the team verified energy‑time entanglement with an average net visibility of 93.1% (each channel >86.0%). The CHSH Bell inequality was violated with S = 2.810 ± 0.028, exceeding 12 standard deviations, confirming high‑quality entangled photon pairs.

The AlGaAs‑on‑insulator platform offers a clear path toward fully integrated, deployable photonic systems. The team is now refining photoresist reflow and dry etching processes to reduce fabrication losses and further improve performance.