A method for estimating the noise of a two-photon entangled state, including generating pairs of photons; for each pair of photons, defining a first polarization measurement, associated with a first angle, and defining a second polarization measurement, associated with a second angle. The method includes generating a first string of polarization measurements and a first string of angles; generating a second string of polarization measurements and a second string of angles; generating a first uncorrelated substring, formed by the polarization measurements of the first string associated with angles that are different from the corresponding angles of the second string of angles; generating a second uncorrelated substring, formed by the polarization measurements of the second string associated with angles that are different from the corresponding angles of the first string of angles; and determining an estimate of the noise on the basis of the first and the second uncorrelated substrings.