Researchers from the University of Science and Technology of China and the Jinan Institute of Quantum Technology have achieved a breakthrough in quantum frequency conversion. The team successfully converted wavelengths from 393nm to 1550nm, setting a new international record for efficiency and noise levels in this band.
The new module achieves an end-to-end efficiency of 28.8 percent, which is approximately 30 times higher than previous efforts. Additionally, the team suppressed pump light noise to 35 counts per second, a reduction of more than two orders of magnitude. These results were published in Physical Review Letters on October 13.
The technology addresses the challenge of transmitting ultraviolet or blue-violet light through fiber optics, which previously limited entanglement distribution to the meter scale. The researchers utilized a quantitative model for domain defect phase perturbation and a method to suppress spontaneous parametric down-conversion noise.
The module has already been applied in long-distance quantum entanglement experiments using 40Ca+ trapped ions. It achieved a signal-to-noise ratio of 120:1, supporting high-fidelity ion-ion entanglement and device-independent quantum key distribution. This development provides a foundation for scalable quantum networks.
