Leakage and correlated errors
Errors outside the computational subspace challenge standard qubit noise models.
Physical intuition
Errors outside the computational subspace challenge standard qubit noise models. This is the starting point for understanding how superconducting circuit parameters determine quantum energy levels and dynamics.
Deep dive: how the mechanism works
Higher transmon levels, crosstalk and common-mode noise produce non-Pauli and correlated errors.
How the quantum phenomenon appears
Leakage-reduction units can remove population from unwanted levels. 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
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.