  Two-photon interference underlies the functioning of many quantum photonics
devices. It also serves as the prominent tool for testing the
indistinguishability of distinct photons. However, as their time-spectral
profile becomes more involved, extracting relevant parameters, foremost the
central frequency difference, may start suffering difficulties. In a parametric
approach, these arise from the need for an exhaustive model combined with
limited count statistics. Here we discuss a solution to curtail these effects
on the evaluation of frequency separation relying on a semiparametric method.
The time trace of the quantum interference pattern of two photons from two
independent solid-state emitters is preprocessed by means of singular spectral
analysis before inspecting its spectral content. This approach allows to single
out the relevant oscillations from both the envelope and the noise, without
resorting to fitting. This opens the way for robust and efficient on-line
monitoring of quantum emitters.
