Extended Data Figure 5: Example of a spin–spin interaction matrix J_ij.

The plot compares theory and experiment. Each element of the J_ij matrix is measured directly (see Methods) in a system of N = 7 spins (solid coloured bars). Overlaid transparent bars with blue edges correspond to the results of a simulation which takes the following experimental parameters into account: the trapping frequencies; frequency of the bichromatic laser beams (see Methods); and measured individual laser–ion Rabi frequencies. The experimental data shown here are the same as in Fig. 1c. The elements J₁₆, J₂₇ and J₁₇ were not measured. Small black vertical lines show one standard deviation in the experimentally measured elements.