Fig. 8: Numerical simulation results for characterizing the controlled phase of a CZ gate with ϕ = π − 0.01, using MEADD and imperfect DD gates.
From: Characterizing coherent errors using matrix-element amplification
a Using the robust DD sequence described in Section “Theory on characterizing two-qubit gate”, the angle of the determinant in Eq. (54), which corresponds to −2nϕ, builds up linearly even if we introduce microwave over-rotation errors on one of the qubits. The strength of the over-rotation, a factor multiplying the π rotation around X, is varied between 0 and 10% and illustrated with the different colors. b Similar simulations now use the XY4 DD sequence, which is not robust to implementation errors in this protocol. c Resulting ϕ-estimate error obtained from fitting the slope of the MEADD data for the different over-rotation errors. The dashed line indicates milliard precision.
