Sub-Rayleigh Imaging via N-Photon Detection

The Rayleigh diffraction bound sets the minimum separation for two point objects to be distinguishable in a conventional imaging system. We demonstrate sub-Rayleigh resolution by scanning a focused beam—in an arbitrary, object-covering pattern that is unknown to the imager—and using N-photon photodetection implemented with a single-photon avalanche detector array. Experiments show resolution improvement by a factor ∼(N-N̅ [subscript max])1/2 beyond the Rayleigh bound, where N̅ [subscript max] is the maximum average detected photon number in the image, in good agreement with theory.United States. Defense Advanced Research Projects Agency (Quantum Sensors program)United States. Army Research Office (MURI grant)Roberto Rocca FoundationW. M. Keck Foundation Center for Extreme Quantum Information Theor