A compact and fast radio-frequency source for efficient Raman sideband cooling.

A compact and fast radio-frequency (RF) source developed for Raman sideband cooling (RSBC) in trapped ion and cold atom experiments is presented. The source is based on direct digital synthesizer, advanced real-time infrastructure for quantum physics, and field programmable gate array. The source has a frequency switching speed of 40 ns and can output continuous μs-level time sequences for RSBC. The maximum output frequency of the source is 1.4 GHz. The RF source is capable of pre-writing data for eight channels. As a demonstration, the RF source is applied to our 25Mg+-27Al+ ion pair optical clock experiment. In order to cool down the ion pair to the vibrational ground state, two-order RSBC is applied to the 25Mg+ ion. As a result, the ion pair motions in the three X, Y, and Z directions are all cooled to the vibrational ground state efficiently, demonstrating the feasibility of this technique. The developed RF source can be widely implemented for other cold atom experiments.