Precise phase estimation has numerous applications, such as measuring displacement, optical path length, refraction index and other material properties. Classically, phase measurement resolution is limited by the Rayleigh-diffraction-limit (RDL) and its precision by the shot-noise-limit (SNL). Using quantum mechanics, one can break these limits. Previous works have shown poor precision enhancement and relative low resolution enhancement. In fact, many works that used states that could break the SNL, did not manage to do so. Here, we present an experiment that can only approach the SNL, but demonstrate a very large resolution enhancement. Using a silicon-multiplier (SiPM) photon-number resolving detector, we measure the photon-number parity of one output of a Mach-Zender interferometer (MZI). Super resolved phase-measurements by a factor up to 300 are demonstrated [1], as well as measurements at the SNL using coherent states with 200 photons on average.

 [1] Gao, Y; Anisimov, PM; Wildfeuer, CF; Luine, J; Lee, H; Dowling, JP. 2010. “Super-resolution at the shot-noise limit with coherent states and photon-number-resolving detectors”.  JOSA B, 27(6), A170-A174 (2010)