Resonant switching current detector based on underdamped Josephson junctions

Current-biased Josephson junctions can act as detectors of electromagnetic radiation. At optimal conditions, their sensitivity is limited by fluctuations causing stochastic switching from the superconducting to the resistive state. This work provides a quantitative description of a stochastic switching current detector, based on an underdamped Josephson junction. It is shown that activation of a Josephson plasma resonance can greatly enhance the detector responsivity in proportion to the quality factor of the junction. The ways of tuning the detector for achieving optimal operation are discussed. For realistic parameters of $\mathrm{Nb}$/${\mathrm{Al}\mathrm{O}}_x$/$\mathrm{Nb}$ tunnel junctions, the sensitivity and noise-equivalent power (NEP) can reach values of $S\simeq 5\times {10}^{12}$ (V/W) and $\mathrm{NEP}\simeq 2\times {10}^{-23}$ (${\mathrm{WHz}}^{-1/2}$), respectively. These outstanding characteristics facilitate both bolometric and single-photon detection in microwave and terahertz ranges.