Fig. 3. Entangling gate between a diagonal ion pair.

a Phase modulation sequence for the LU ion pair. We alternatingly apply the driving laser on the two target ions, indicated by the color of the bars, with a fixed laser detuning μ_LU = (ω₂ + ω₄)/2. Each segment takes time t = 4π/(ω₂ − ω₄) with the laser phase given by the height of the bars. We set a separation Δt = 2 μs between adjacent segments to turn the driving laser off and on, so as to avoid crosstalk during the switching. b Theoretical phase space trajectories for the four phonon modes when the spin state is $∣++⟩$. Different segments are indicated by different colors. c Similar plot as Fig. 2d, e for the LU ion pair. A gate infidelity of 4.0(3)% is fitted. d Similar plot as Fig. 2c for theoretically simulated gate errors. All the error bars represent one standard deviation.