Extended Data Fig. 8: QFI.

Normalized QFI for a Néel state (N = 15) with g/J₀ = 0.24 (white) and g/J₀ = 2.4 (blue), corresponding to the lowest- and highest-gradient data in Fig. 2d. Points are experimental observations, averaged over 200 repetitions, with lines as guides to the eye. A value greater than one (dashed line) is an entanglement witness. After the initial fast dynamics up to tJ₀ ≈ 1, the QFI is consistent with saturation for the small gradient, and with slow entanglement growth for the large gradient, with behaviour very similar to that previously observed in disordered MBL³⁰.