Fig. 5: Landau-Zener-Stückelberg (LZS) interference.

a Schematic showing the electric-field generated by the MW drive, connecting the bond wire and ground plane (dark grey, not drawn to scale), which can generate significant stark shifts. b Sequence, as in Fig. 4a, but now explicitly including the electric field (E_MW). c Characteristic LZS interference pattern (theory) as function of the laser detuning, and the electric field strength A. At higher electric fields, side bands emerge at multiples of the driving frequency ω = 70 MHz. d Line cut through (c) for A = 118 MHz. The dashed line denotes an example threshold T. e The experimental spectrum expected from the situation in (d). The signal differs from the original spectrum as it is weighted over the probability to pass the threshold for different detuning. f Mean detected counts as a function of the two-laser detuning when the MW amplitude is set to 6.5 V, approximately equal to the value in (d). The threshold (T = 10) is set to about half the maximum amplitude, as in (d). The fit function (solid line) is obtained by fitting the dataset for a range of threshold values (see Supplementary Fig. 6). g Same dataset as in (f), but with T = 20. The signal distortion due to the threshold is well-captured by the fit. h Experimental data (grey) and fit (solid lines) as in (f), varying the applied voltage (T = {6, 10, 13, 15}). Data are offset by 10 counts for clarity. i Extracted electric field strength A as a function of the applied voltage. The solid grey line is a linear guide to the eye. j Extracted optical Rabi frequency Ω. Solid grey line denotes the inverse-variance weighted mean. k Extracted optical coherence time T₂. The shaded region denotes the mean lifetime limit: T₂ = 2T₁ ≈ 17 ns. Solid grey line denotes the inverse-variance weighted mean of the data points.