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 to 6.8 nanoseconds while maintaining fidelity.

Transmon Qubit Weak Anharmonicity Limits Gate Fidelity

Analytical construction of quantum gate pulses must account for transitions beyond the primary computational states to achieve high fidelity. Transmon circuits, favored for their scalability, are inherently weakly anharmonic oscillators, and previously unnoticed two-photon transitions now dominate error rates after single-photon leakage is suppressed. The research details how conventional error mitigation strategies falter as quantum processors become more sophisticated and gate times shrink.