Fig. 3: Reconstruction procedure and results of three-qubit CCZS gate.

a Reconstruction procedure for QPT. Standard QPT is first performed to collect the 64 × 27 datasets comprising the reconstruction. Separately, single-qubit GST is performed to extract the noisy groundstates, rotation gates, and POVMs for the three qubits, which are used in the reconstruction to separate SPAM errors. b The ideal unitary of \({U}_{CCZS}(\frac{\pi }{2},\frac{\pi }{2},0)\) and the leading Kraus (LK) matrix obtained from the Kraus operators. The LK matrix captures the majority of the dynamics of a noisy channel⁶². c Bootstrap distributions for a chosen SWAP angle of \(\phi =\frac{\pi }{2}\) over N_boot = 1000. The “raw” process fidelity compares against the target unitary, whereas the control-error-free fidelity mitigates for imperfections in the U_CCZS(θ, ϕ, γ) calibration. d Coherence limit of the three-qubit gate given the T₁, T₂ values with 95% confidence interval (see Supplementary Note 5), the raw fidelity of the reconstruction, and the control-error-free fidelity with 2σ error.