Extended Data Fig. 1: Theoretical prediction for density-contrast correlation functions in real space.

The initial temperature is taken to be 40 nK, the final speed of sound is 1.2 µm ms⁻¹ and the ramp goes from a_s = 350a_B to a_s = 50a_B with scale factor a(t) ∝ t^γ for a decelerated expansion with γ = 0.5 and a duration ∆t = 1.5 ms (left) and ∆t = 3.0 ms (right). The fields are convoluted with a Gaussian of σ = 0.8 µm corresponding to the optical resolution of the experiment. Different colours correspond to different hold times.