Two-qubit RB (orange) and two-qubit interleaved RB (purple), for all pairs of nuclear spins, corresponding to the same pairs of spins studied in d. The physical CZ gate fidelities (Fcz²³) are calculated from the non-interleaved reference Clifford fidelities (FC,ref²³) and the interleaved Clifford fidelities (obtained from the fits to the purple data points). The errors are obtained from the least-square fits at a level of 1 s.d. The physical CZ gate fidelities for all pairs of nuclear spins are above the fault-tolerant threshold. Avg., average.
