Extended Data Figure 3: Bounds on macroscopic extensions of quantum mechanics.

Exclusion curves for the minimal modification to quantum mechanics proposed in ref. 4. Points in this parameter space below a given curve in the plot have been ruled out by the corresponding experiment. The green curves show the bounds placed by the 2ħk and 90ħk atom interferometry results presented in this work. The grey, shaded area illustrates the region of parameter space excluded by these results. For sub-micrometre critical lengths, affected atoms would receive sufficiently large spontaneous momentum kicks to move out of the interferometer output ports. This results in atom loss and in a reduced sensitivity of the interference contrast to the decoherence rate. Therefore, we cut off the curves arising from our interferometry data at 1 μm. We also show exclusion curves from a sodium interferometer from 1992⁴⁰ (solid black), a caesium interferometer from 2001³⁷ (solid red), a neutron interferometer from 2002⁴¹(dashed red), a C₇₀ molecular interferometer from 2002⁴² (dashed black), a caesium interferometer from 2009³⁸ (solid blue), a caesium interferometer from 2012³⁹ (dashed blue), a C₂₈₄H₁₉₀F₃₂₀N₄S₁₂ molecular interferometer from 2013⁴³ (solid orange), and a rubidium interferometer from 2013²⁵ (solid cyan). For all of the exclusion curves, the change in slope occurs at a critical length scale value equal to the wave packet separation.