We present the experimental demonstration of a superconducting photon number resolving detector. It is based on the series connection of N superconducting nanowires, each connected in parallel to an integrated resistor. The device provides a single voltage readout, proportional to the number of photons absorbed in distinct nanowires. Clearly separated output levels corresponding to the detection of n=1-4 photons are observed in a 4-element detector fabricated from an NbN film on GaAs substrate, with a single-photon system quantum efficiency of 2.6% at the wavelength of 1300nm. The series-nanowire structure is promising in view of its scalability to large photon numbers and high efficiencies.
@article{arxiv.1203.5477,
title = {Photon-number resolving detector based on a series array of superconducting nanowires},
author = {Saeedeh Jahanmirinejad and Giulia Frucci and Francesco Mattioli and Dondu Sahin and Alessandro Gaggero and Roberto Leoni and Andrea Fiore},
journal= {arXiv preprint arXiv:1203.5477},
year = {2015}
}