Mitigating crosstalk errors in single-qubit gates on a superconducting quantum processor using analytical control pulse shaping: part 2

Superconducting quantum processor topologies with square connectivity benefit greatly from the ability to perform parallel single and two-qubit operations. Microwave and hybridization crosstalk often limit the fidelity of simultaneous single-qubit gates in transmon-based quantum processing units (QPUs) due to crosstalk-induced errors in the qubit subspace and leakage to higher states. Here, we quantify the impact of single qubit errors due to crosstalk in terms of error landscapes using statistics of crosstalk on IQM's crystal-50 QPU. We then optimize the pairwise detuning based on measured crosstalk values to demonstrate average 99.96(1)% simultaneous gate fidelity approaching individual gate fidelities for 16ns sqrt(𝑋) gates. Finally, we reduce the required qubit frequency bandwidth using two pulse shaping techniques—HD DRAG and strongly off-resonant control pulses— discussed in part 1 of this talk. The demonstration of analytical pulse-shaping techniques to mitigate crosstalk errors on larger than few-qubit devices is key to demonstrate their viability as part of an efficient model-based calibration toolbox. In the future, the methods demonstrated here can coexist with other crosstalk-mitigation techniques, such as active cancellation, to reduce costly hardware requirements at scale.