Thermal Activated Escape In Josephson Junctions

This thesis reports on my recent experimental research in Nanjing University. In Chapter 1, I first present the basic conception of thermal activation to help the readers to understand the rest of the thesis. Then I introduce the ideas of using the superconducting Josephson Junctions as an experiment device for classic thermal activation.In Chapter 2,1 present the experiment system for superconducting Josephson Junctions including the 4.2K liquid helium and the cryogen-free dilution refrigerator. This part also contains the details of the process of setting up experiment device. The second part of this chapter is the detecting methods of the Josephson Junctions such as the switching current distribution and additional noise.In Chapter 3, I present the experiment data of the stochastic resonance in Josephson Junctions. We observed the phenomenon of two kinds of stochastic resonance in Josephson junction. One is caused by the fluctuation of the potential barrier and the other is by the fluctuation of the temperature.In Chapter 4, I present the research of the phase-diffusion observed in the underdamped Josephson junction. The phenomenon of phase-diffusion occur both in the process of Josephson junction switch from superconducting state to normal resistance state and the transition from finite voltage state to zero voltage state.