Tunnel Junction as a Noise Probe

The paper investigates theoretically effects of noise on low-bias parts of IV curves of tunnel junctions. The analysis starts from the effect of shot noise from an additional (noise) junction on the Coulomb blockaded Josephson junction in high-impedance environment. Asymmetry of shot noise characterized by its odd moments results in asymmetry of the IV curve of the Josephson junction. At high currents through the noise junction the IV curve is sensitive to electron counting statistics. The theory is generalized on another type of noise (phase noise of a monochromatic AC input) and on a normal Coulomb blockaded tunnel junction. The effect of shot noise on the IV curve of a superconducting Josephson junction in low-impedance environment is also analyzed. From this effect one can obtain information on the time necessary for an electron to tunnel through the junction responsible for shot noise. In summary, the analysis demonstrates, that the low-bias part of the IV curves of tunnel junctions can be a sensitive probe of various types of noise.