ObjectiveImplementation of quantum network requires the transmission of information between the same or different quantum nodes through the fiber channel. Cesium atom nodes are significant quantum resources, and thus it is essential to connect cesium atom systems with optical fiber channels. The frequency of photons directly emitted by common quantum nodes has great loss in fiber channel and is not suitable for transmission in fiber, so quantum frequency conversion becomes the key technology. In quantum frequency conversion, due to the counts of noise photons are much higher than that of the target photons, signal-to-noise ratio cannot be ignored. Therefore, enhancing the signal-to-noise ratio in quantum networks is a paramount issue.MethodsWe intend to achieve 852 nm photons conversion to 1560 nm photons based on waveguide, and analyzed noise photons induced by the strong pump laser at different wavelength, such as spontaneous parametric down conversion, spontaneous Raman scattering and cascaded difference frequency generation. An acoustic-optical modulator and a strong attenuator are employed to chop and attenuate the 852 nm continuous-wave laser to 2.5 MHz repetition rate with low intensity. To enhance the signal-to-noise ratio of the target photons, a combination of changing polarization of noise photons in the difference frequency generation process and using the narrow-band filters is employed, the photonic wave packets before and after the conversion are character-ized by single photon detector. Finally, Connecting the optimized magneto-optical trap system to the frequency conversion device.Results and DiscussionsIn this paper, we first measured the optimal matching temperature of the waveguide is 36.6 ℃. Then filters with different bandwidths are employed, including a 50 nm bandwidth bandpass filter, a 12 nm bandwidth bandpass filter and a 0.3 nm bandwidth fiber bragg grating. The experimental results indicate that as the bandwidth of filters decreases, the signal-to-noise ratio significantly improves. When the 0.3 nm bandwidth fiber bragg grating and the 12 nm bandwidth bandpass filter are used, the signal-to-noise ratio can be increased to 91.3. If a filter with an even narrower bandwidth is selected, the noise photons near the target photons will be further suppressed. The internal conversion efficiency of the waveguide reaches 6.2% when the pump light power is 400 mW. Finally, the photonic wave packets before and after the frequency conversion are identical, indicating that the frequency conversion does not affect the photonic wave packets. Using feedback loop control, we load multiple atoms into the magneto-optical trap, the photons counts are 16000 counts/50 ms, the maximum SNR is approximately 2.ConclusionsBased on the above waveguide frequency conversion system, we aim to establish a connection between the cesium atom systems and the optical fiber communication band, ensuring that the photonic wave packets remain unchanged before and after the conversion. This allows photons to retain their original information after long-distance transmission, thereby providing a foundation for constructing quantum networks with hybrid nodes.