Direct Experimental Certification of Quantum Non-Gaussian Character and Wigner Function Negativity of Single-Photon Detectors

Highly nonclassical character of optical quantum detectors, such as single-photon is essential for preparation states light and a vast majority applications in metrology information processing. Therefore, it both fundamentally interesting practically relevant to investigate the features measurements. Here we propose experimentally demonstrate procedure direct certification non-Gaussianity Wigner function negativity, two crucial nonclassicality levels, photonic detectors. Remarkably, characterize highly properties detector by probing with only classical thermal vacuum state. We avalanche diode even under presence background noise, also certify negativity this detector. Our results open way benchmarking detectors few measurements on states.