Investigating Single-Qubit Gate Speed and Fidelity

For superconducting qubits, fast gates are necessary to increase the circuit depth or the total number of operations before decoherence decreases the state fidelity. This is done by applying short, high-power microwave pulses resonant with the qubit. However, as gate time decreases, shorter pulses encompass a larger frequency bandwidth. In transmon qubits, this increases leakage out of the computation subspace because of the qubit's relatively small anharmonicity. This unwanted leakage can be mitigated using well-known techniques such as pulse-shaping and derivative removal by adiabatic gates (DRAG). Modern hardware allows for fast, arbitrary control over pulse envelopes enabling the use of new gate-error mitigation strategies. To explore improvements to single qubit gates, we investigate qubit leakage and gate fidelities in planar transmon devices. We compare measured qubit gate speed and fidelity while using these common leakage-mitigation schemes and compare our results to those obtained using new mitigation techniques.