Quantum characterization of superconducting photon counters
  We address the quantum characterization of photon counters based on transition-edge sensors (TESs) and present the first experimental tomography of the positive operator-valued measure (POVM) of a TES. We provide the reliable tomographic reconstruction of the POVM elements up to 11 detected photons and M=100 incoming photons, demonstrating that it is a linear detector. 
Giorgio Brida, Luigi Ciavarella, Ivo P. Degiovanni, Marco Genovese,   Lapo Lolli, Maria G. Mingolla, Fabrizio Piacentini, Ma...
quant-ph cond-mat.supr-con