Fig. 4: Dependence of the trace of inverse FIM on the normalized slit size d/dR.

The results are shown for detection of nth-order correlations (blue dotted lines), (n − 1)th-order correlations (green dashed lines), and (n − 1)th-order correlations, conditioned by detection of the nth photon in the region \({{\Omega }}=\{{{{\bf{k}}}}:{k}_{\max }\le | {{{\bf{k}}}}| \le 2{k}_{\max }\}\) (black solid lines) and \({{\Omega }}=\{{{{\bf{k}}}}:{k}_{\max }\le | {{{\bf{k}}}}| \le 1.5{k}_{\max }\}\) (red dot-dashed lines) for n = 4 (a, b), 3 (c, d), and 2 (e, f). The objects, shown in Fig. 3a (for plots a, c, and e) and Fig. 3c (for plots b, d, and f), were decomposed in terms of 10 basis functions, representing slit-like pixels with equal widths d. The object size, the basis functions widths, and the step of the signal sampling points were scaled in the same way with d. Horizontal dotted lines indicate the threshold \({{{\rm{Tr}}}}{F}^{-1}\le {N}_{\max }=1{0}^{5}\), used for quantification of resolution. For comparison, panels b, d, f also show (by double-dot-dashed purple lines) the trace of inverse FIM for traditional coherent-light imaging for detection of 10⁸ photons (instead of a single coincidence event for all other lines).