Linearity and scalability of photon counting: toward accurate multiparameter photonic sensing

We introduce the direct linearity characterization of single-photon detectors and photon-number-resolving detectors. We discuss the supralinearity that goes beyond the current single-photon detection models. We also report on advanced detectors and sensors of statistical, vector, and correlation properties of light down to the single-photon level. The novel detection schemes harness complex optical networks, single-photon detector arrays, and deep learning. We present high-fidelity photon statistics estimation, resource-efficient polarization sensor, and quantum entanglement detector. We discuss the efficiency and scaling of the presented detection modalities.