Figure | Scheme of quantum-enhanced phase retrieval. Quantum correlation are produced in a non-linear crystal by the phenomenon of Spontaneous Parametric Down Conversion (SPDC) in which some of the photons from a laser beam (PUMP) are converted pairs of perfectly correlated photons emitted along distinct but correlated directions. Accumulating a large number of these pairs generates two quantum correlated beams, the signal (s) and idler (i) ones. The signal beam is used to probe the sample, then it is measured by the pixels of a low-noise CCD Camera as it would happen in a conventional scheme. L1 and L2 are lenses. The idler beam is a perfect replica of the signal one, it is measured separately and serves as a reference for the intensity fluctuation that can be subtracted from the signal pixel-to-pixel. The sample is measured in two different axial positions, and the intensity images corrected for the noise are then used for the retrieval of the phase profile.