Extended Data Fig. 3: State-preparation errors for 1D chain.

Site-resolved population measurements for different initial state preparations at various angles θ relative to the quantization axis, showing the initial state-preparation error. The detection error is corrected through the maximal likelihood method, using the cost function of equation (4). a–c, Population distributions for an initial Néel state with four holes in the centre at θ = 30° (a), θ = 45° (b) and θ = 54° (c). d–f, population distributions for different numbers of holes at θ = 51.7°: one hole (d), two holes (e) and four holes (f). g–j Population distributions for different magnetic backgrounds: AFM along z at θ = 49.7° (g) and θ = 59.7° (h) and AFM and FM along x (i,j). The measured populations are shown for the four possible states: ground state (black), |↓⟩ (red), |h⟩ (white) and |↑⟩ (blue). These errors are systematically included in all of the numerical simulations presented in the main text.