PT Journal
AU Polyakova, M
   Semenov, AV
   Kovalyuk, V
   Ferrari, S
   Pernice, WHP
   Gol'tsman, GN
TI Protocol of measuring hot-spot correlation length for SNSPDs with near-unity detection efficiency
SO IEEE Trans. Appl. Supercond.
JI IEEE Trans. Appl. Supercond.
PY 2019
BP 1
EP 5
VL 29
IS 5
DI 10.1109/TASC.2019.2906267
DE SSPD; waveguide-integrated SNSPD; hot-spot interaction length
AB We present a simple quantum detector tomography protocol, which allows, without ambiguities, to measure the two-spot detection efficiency and extract the hot-spot interaction length of superconducting nanowire single photon detectors (SNSPDs) with unity intrinsic detection efficiency. We identify a significant parasitic contribution to the measured two-spot efficiency, related to an effect of the bias circuit, and find a way to rule out this contribution during data post-processing and directly in the experiment. From the data analysis for waveguide-integrated SNSPD, we find signatures of the saturation of the two-spot efficiency and hot-spot interaction length of order of 100 nm.
ER