Chinese Researchers Link Trapped-Ion Quantum Memory with Telecom Fiber

People's Daily reported that a research team from the University of Science and Technology of China, including Pan Jianwei and Zhang Qiang, alongside Zheng Mingyang from the Jinan Institute of Quantum Technology, achieved high-efficiency, low-noise quantum frequency conversion between 393 nanometers and 1550 nanometers. Published in Physical Review Letters, the work set new international records for conversion efficiency and noise levels in this wavelength band, providing key technology to link trapped-ion nodes in scalable quantum networks. To resolve prior performance barriers, the researchers developed and validated a quantitative theoretical model detailing how domain-defect phase perturbations reduce conversion efficiency. The team also uncovered inverse tuning characteristics between short-wavelength pumped frequency conversion and spontaneous parametric down-conversion noise, which allowed them to establish a method that substantially suppressed pump light noise. Using these methods, the team constructed a conversion module operating from 393 nanometers to 1550 nanometers that achieved an end-to-end efficiency of 28.8% and reduced pump noise to 35 per second. Compared with earlier research, the device improved efficiency by approximately 30 times and lowered noise by more than two orders of magnitude, establishing a new record for this frequency conversion band.

The frequency conversion module has already been deployed in long-distance quantum entanglement using trapped calcium ions, delivering a signal-to-noise ratio up to 120:1. This performance supported experimental demonstrations of long-lived, high-fidelity remote ion-ion entanglement alongside device-independent quantum key distribution, providing a key device foundation for scalable quantum repeaters and wide-area networks.