Quantum Control with DRAG Pulses

Derivative-shaped controls that suppress leakage and phase errors in weakly anharmonic qubits. The main concepts are DRAG quadrature, calibration, leakage. Each must be defined in the context of a concrete physical model, mathematical representation, or experimental task. Terminology alone does not establish the behavior of the system.

DRAG control uses a derivative quadrature component to reduce population leakage from a weakly anharmonic computational transition into unwanted excited levels. Its optimal coefficient depends on anharmonicity, detuning, pulse bandwidth and the chosen carrier and rotating-frame conventions. A Gaussian envelope with an arbitrary derivative is not automatically a calibrated DRAG pulse.

Derive a three-level driven Hamiltonian, sweep in-phase and quadrature amplitudes, and compare leakage-sensitive measurements to an independently calibrated two-level rotation. Validate pulse distortion, mixer imbalance, detuning and repeatability before reporting a gate fidelity. Coherent calibration error and stochastic dephasing should be estimated separately.