Recursive DRAG cuts qubit errors by accounting for higher levels

Transmon circuits, the foundation of many quantum processors, are increasingly susceptible to errors from unwanted transitions to higher energy levels as control drives become more precise. Researchers have demonstrated that after suppressing single-photon leakage, transitions between the |0⟩ and |2⟩ states and between |1⟩ and |3⟩ become the dominant sources of qubit error, an issue previously unaddressed by existing error mitigation strategies. To counter this, the team constructed recursive DRAG-type corrections that simultaneously suppress both single- and two-photon leakage, achieving gate fidelity of 99.999% for an 11.8 nanosecond pulse. This work extends beyond analytical construction to provide a systematic understanding of calibration parameters, reducing gate time…