Estimating the Photon-Number Distribution of Photonic Channels for Realistic Devices and Applications in Photonic Quantum Information Processing

Characterising the input-output photon-number distribution of an unknown optical quantum channel is important task for many applications in information processing. Ideally, this would require deterministic sources and photon-number-resolving detectors, but these technologies are still work-in-progress. In work, we propose a general method to rigorously bound photon number using standard devices such as coherent light non-photon-number-resolving detectors/homodyne detectors. To demonstrate broad utility our method, consider security analysis practical key systems based on calibrated single-photon detectors experimental proposal implement time-correlated single counting technology homodyne instead