Compensation of power line-induced magnetic interference in trapped-ion system

The low-frequency magnetic interference induced by the laboratory power supply is one of the main decoherence sources of trapped-ion qubits. Synchronizing the experimental sequence with the phase of power line is widely used to mitigate this problem, but this results in a significant decrease in experimental efficiency. In this paper, we experimentally demonstrate a simple active compensation method to reduce the observed 50 Hz and 150 Hz strong magnetic interference in an ion trap induced by the power line. In our method, a single ^40 Ca^+ ion is used as the magnetic probe and an reverse compensation signal is generated by a programmable arbitrary waveform generator (AWG). After compensation, an 86 % reduction of the periodic magnetic field fluctuation and over 35-fold extension of the coherence time from 70 to 2500 s were observed. This method can also be applied to suppress other spectral components of the magnetic field fluctuation related to the power line, and it is also useful for other atomic systems such as neutral atoms.