Concept 28 of 42 · Control and Entangling Gates

DRAG pulse shaping

Quadrature shaping suppresses leakage from weakly anharmonic qubits.

01 / Mathematical framework
$$\Omega_Q(t)\propto-\frac{\dot\Omega_I(t)}{\alpha}$$

Physical intuition

Quadrature shaping suppresses leakage from weakly anharmonic qubits. This is the starting point for understanding how superconducting circuit parameters determine quantum energy levels and dynamics.

Deep dive: how the mechanism works

An auxiliary quadrature approximately cancels unwanted excitation of higher levels.

How the quantum phenomenon appears

Transmon X gates often use calibrated DRAG corrections. To establish the predicted quantum behavior, connect the circuit Hamiltonian to a measured transition, coherence experiment, gate benchmark or calibrated readout signal.

Assumptions and limitations

Optimal coefficients depend on device model, detuning and bandwidth.

Research and simulation exercise

Identify the tunable parameters, predict the observable from the stated model, and sweep one parameter while holding the others fixed. Compare against a simpler reference model, quantify loss and uncertainty, and state which observations would falsify the hypothesis.

Connect the ideas

See the chapter guide and further reading.

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