Validating the calibrated creation of heralded single photons
Coincidence-count discrimination is a practical and straightforward tool for the characterization of photon-pair processes and heralded single photons. Here, we implement a heralded single photon source based on parametric down-conversion in a periodically poled KTiOPO$_4$ waveguide in the telecom wavelength range involving a low number of optical modes. We extend the toolbox for the loss-tolerant state characterization by combining conventional figures-of-merit in order to access the heralded state's mean photon number and its photon-number parity. Our experiment demonstrates that an accurate determination of these characteristics is possible just through simple photon-correlation measurements. We believe that our results can find usage in the calibrated creation of heralded single photons and in determining the expectation values of observables that are crucial for attributing a single quantum.