Error landscapes over frequency offsets of motional center-of-mass (c.m.) and tilt modes, simulated for robust FM and b-robust FM pulses. The regions where the error is lower than 10−3 are marked with dashed contour lines. The b-robust pulse is clearly more robust over a wider region of offsets.
Two-qubit gates in trapped-ion quantum computers are generated by applying spin-dependent forces that temporarily entangle the internal state of the ion with its motion. Laser pulses are carefully designed to generate a maximally entangling gate between the ions while minimizing any residual entanglement between the motion and the ion. The quality of the gates suffers when the actual experimental parameters differ from the ideal case. Here, we improve the robustness of frequency-modulated Mølmer-Sørensen gates to motional mode-frequency offsets by optimizing the average performance over a range of systematic errors using batch optimization. We then compare this method with frequency-modulated gates optimized for ideal parameters that include an analytic robustness condition. Numerical simulations show good performance up to 12 ions, and the method is experimentally demonstrated on a two-ion chain. doi 10.1103/PhysRevApplied.16.024039
Mingyu Kang, Qiyao Liang, Bichen Zhang, Shilin Huang, Ye Wang, Chao Fang, Jungsang Kim, and Kenneth R. Brown
