Fig. 2
From: Bell correlations between spatially separated pairs of atoms
Tunable momentum-spin anti-correlated atomic pair source. a Schematic of atoms with momentum and spin degrees of freedom in the scattering sphere. A 2D planar slice in momentum space is taken for simplicity. b Two-body cross-correlation function in momentum-spin \({g}_{\uparrow \downarrow }^{(2)}\) from the un-rotated pair source with an average mode occupancy of \(n=0.058(2)\), averaged over 2100 experimental runs. c The dependence of the degree of anti-correlation on the average halo mode occupancy. Two different angles between the Raman beams (\(3{0}^{\circ }\) and \(9{0}^{\circ }\)) were used to produce the experimental data. The dashed line depicts the theoretical prediction. Demonstration of Bell nonlocality strictly requires \({g}_{\uparrow \downarrow }^{(2)}\ > \ 3+2\sqrt{2}\) (shaded region), based on a fully QM prediction for the violation of CHSH inequality18. All error bars indicate the standard error in the mean
