Figure 4
From: Hybrid setup for stable magnetic fields enabling robust quantum control
Sensing of oscillating magnetic fields originating from stray radio-frequency currents. Detection of variations of field strength Bosc via spin-echo sequences that record phase accumulation from induced differential (frequency dependent) a.c. Zeeman shifts, while the ion is in a superposition state of \(|\mathrm{3,1}\rangle \) and \(|\mathrm{2,0}\rangle \). For fields oscillating at Ωosc = ΩRF = 2π × 57.3 MHz and our setup, we calculate a quadratic sensitivity of 2π × 4.783 Hz μT−2. Pulse sequences of the spin-echo experiments varying ΔURF and the ion position along y respectively, times not to scale. (a) Differential a.c. Zeeman shifts ΔωMW, 2 as a function of ΔURF, i.e., systematic variation of stray currents ∝ URF. Uncertainties of data points are smaller than the markers. We find a slope of 2π × 20.77(7)mHzV−2 from a model fit and conclude Bosc = 5.239(8) μT for our typical operation condition URF = 79.5 V. (b) Spatial variation of Bosc along the y direction. Data is in agreement with a model fit with a slope of \(\delta {B}_{osc}/\sqrt{(\delta y)}\) = 0.262(3) μT μm−1/2.
