Fig. 2. Experimental HOM dips (left axis) are shown for various visibilities, introduced by a differential polarization change.

The estimated total Fisher information NF (Eq. 2; right axis, red) along with the inverse variance of our experimental estimates are shown (gray crosses, right axis). The rightmost panel includes theoretical curves for perfect visibility, where the two peaks in the Fisher information have asymptotically merged. The open circle denotes a point where the Fisher information is undefined.