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Fano fluctuations in superconducting nanowire single-photon detectors



Alex Kozorezov, Colin Lambert, Francesco Marsili, Marty Stevens, Varun Verma, Matthew Shaw, Richard Mirin


Because of their universal nature, Fano fluctuations are expected to play an important role in the behavior of superconducting nanowire single-photon detectors (SNSPDs). Taking into account Fano fluctuations we predict that the photon counting rate as a function of bias current in narrow-wire SNSPDs is described by a complementary error function. The finite width of this function, sigma, arises from fluctuations in the energy partition between quasiparticles and phonons during the energy down-conversion cascade. In narrow-wire, spatially homogeneous SNSPDs, the effect of Fano fluctuations on sigma is dominant, while in wide-wire SNSPDs it will account for a substantial part of the transition width acting independently in parallel with vortex-related mechanisms. We demonstrate good agreement between theory and experiments for a series of bath temperatures and photon energies in narrow WSi SNSPDs. The time-resolved two-photon photoresponse count rates predicted by Fano fluctuations match the Lorentzian shapes observed in experiments over the whole range of bias current for the two-photon detection regime.
Physical Review B


single photon detectors, superconductors, Fano fluctuations


Kozorezov, A. , Lambert, C. , Marsili, F. , Stevens, M. , Verma, V. , Shaw, M. and Mirin, R. (2017), Fano fluctuations in superconducting nanowire single-photon detectors, Physical Review B, [online], (Accessed May 23, 2024)


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Created August 9, 2017, Updated May 5, 2023