A quantum frequency converter cuts noise to 35 counts per second

Researchers of China have achieved an ultra-low noise level of 35 counts per second in a quantum frequency converter, a reduction critical for extending the reach of future quantum communication networks. The device efficiently converts ultraviolet photons to the telecom C-band, wavelengths already used in existing fiber optic infrastructure. This advance, detailed in Nature, combines fabrication optimization with a noise suppression strategy, resulting in a record-high external efficiency of 28.8%. This high-performance quantum frequency conversion satisfies the stringent requirements for long-lived remote ion-ion entanglement in scalable quantum networks. A newly demonstrated quantum frequency converter achieves an external efficiency of 28. The conversion process relies on a first-order quasi-phase matching period of 3. 07 micrometers, a precise structural requirement for efficient frequency mixing. Theoretical modeling played a large part in optimizing the converter’s performance, revealing a critical tolerance for domain defects within the lithium niobate waveguide. Researchers found that domain…