Noise of a superconducting photon detector

We have studied electrical noise of photon detectors representing long and narrow superconducting strips. For large bias currents close to the critical current fluctuations lead to localized, temporary transitions into the normal conducting state, which can be detected as voltage transients developing between the strip ends. We present models based on fluctuations of the chemical potential and current-assisted thermal-unbinding of vortex-antivortex pairs, which explain the current and temperature-dependence of the detector noise.