Coulomb-Blockaded Josephson Junction As A Noise Detector

The behavior of a Josephson junction is strongly influenced by the dissipation caused by the resistance R of the surrounding environment. If dissipation is small (R > RQ = h/4e ), the phase of the junction becomes delocalized by fluctuations, and Coulomb blockade (CB) of Cooper pair tunneling takes place. In this case, theory predicts a power-law-like increase of conductance, both as a function of temperature and voltage. The exponent of the power law, 2ρ − 2, is specified by the parameter ρ = R/RQ. Hence, in the case of large exponents 2ρ − 2 1, the conductance is highly susceptible to tiny changes in temperature, or alternatively, there is a high sensitivity to any extra noise sources. We have investigated if this extreme sensitivity could be turned into use in a high-resolution noise detector. For this purpose, we have experimentally investigated how the CB of a Josephson junction changes in the presence of shot noise induced by a near-by SIN junction. In this brief note, we will discuss just one of our samples and present the basic findings on it. For a more detailed description, we refer to a forthcoming publication Ref.