“…With knowledge of the joint spectral amplitude, we can extract information about the different degrees of freedom of the photon pairs and their quantum correlations. To date, measurement of the properties of the joint spectral amplitude and its magnitude [12,[17][18][19][20] has been nontrivial, typically relying on single-photon detection, which results in slow characterization and low resolution. Recently, a simple relation between spontaneous and stimulated emission of photon pairs in second-order nonlinear materials was demonstrated theoretically [21], implying that the joint spectral amplitude of photon pairs that would be generated in the spontaneous process can be measured through the corresponding stimulated process.…”