Characterization of superconducting nanowire single-photon detector with   artificial constrictions
  Statistical studies on the performance of different superconducting nanowire single-photon detectors (SNSPDs) on one chip suggested that random constrictions existed in the nanowire that were barely registered by scanning electron microscopy. With the aid of advanced e-beam lithography, artificial geometric constrictions were fabricated on SNSPDs as well as single nanowires. In this way, we studied the influence of artificial constrictions on SNSPDs in a straight forward manner. By introducing artificial constrictions with different wire widths in single nanowires, we concluded that the dark counts of SNSPDs originate from a single constriction. Further introducing artificial constrictions in SNSPDs, we studied the relationship between detection efficiency and kinetic inductance and the bias current, confirming the hypothesis that constrictions exist in SNSPDs. 
Ling Zhang, Lixing You, Dengkuan Liu, Weijun Zhang, Lu Zhang, Xiaoyu   Liu, Junjie Wu, Yuhao He, Chaolin Lv, Zhen Wang, and ...
cond-mat.supr-con