Fig. 6: Experimental results of MEADD for interleaved single-qubit X(−π/2) and X(π) gates.
From: Characterizing coherent errors using matrix-element amplification
a CAFE results for the single-qubit unitaries characterized by MEADD (blue) compared to assuming a perfect gate (gray) for 69 qubits of a single Sycamore device. The cycle circuit being repeated in CAFE is the same as in the MEADD protocol, namely a X(−π/2) rotation followed by a X(π) rotation, performed in parallel on all qubits. Solid lines with markers are the median over the 69 qubits, and the shaded regions are the inner quartile regions. b Distributions of the characterized relative rotation axis parameter ζ = χπ/2 − χπ defined in Eq. (24) for a representative single-qubit gate characterized 32 times interleaved between MEADD (blue) and 4-axis tomography (orange), using the same number of measurements for both methods. c Distributions of run-to-run standard deviations in ζ estimates for the two methods over the 32 sequential characterizations of the 69 qubits. The median standard deviations of the two methods are reported in milliradian.
