State-independent quantum state tomography by photon-number-resolving measurements

Complete and accurate quantum state characterization is a key requirement of quantum information science and technology. The Wigner quasi-probability distribution function provides such a characterization. We reconstructed the Wigner function of a narrowband single-photon state from photon-number-resolving measurements with transition-edge sensors (TESs) at system efficiency 58(2)%. This method makes no assumption on the nature of the measured state, although a limitation on continuous-wave photon flux was imposed by the TES. The negativity of the Wigner function was observed in the raw data without any inference or correction for decoherence. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement