project title: Josephson junction threshold detectors of current fluctuations
project leader: Hermann Grabert
access given (in days): 31
access used (in days): 13
local host: Jukka Pekola
home institution: University of Freiburg
country of institution: Germany
starting date (yyyy-mm-dd): 2006-03-26
The group at Freiburg has been working for a long time on the problem of decay of a metastable state. The results can be applied to the case of escape of a Josephson junction from superconducting into resistive state. This escape is very sensitive to the fluctuations in bias current of the junction, and therefore it makes a Josephson junction a suitable detector of shot noise and full counting statistics (FCS). Hermann Grabert and Joachim Ankerhold from Freiburg have been working on the theory, based on Fokker-Planck approach, on how FCS influences this decay. There are other approaches, for example a fully quantum mechnical method and an adiabatic method. The full picture is not clear but the experiments start to shed light on this issue. This project is aiming to further intensify discussion on this topic and to streamline the theoretical picture.
Dr. Joachim Ankerhold visited LTL in August 2006 and the problem of full counting statistics measurement using a Josephson junction detector was discussed in depth. This work has now resulted in two papers, one theoretical one [J. Ankerhold, Phys. Rev. Lett. 98, 036601 (2007)] and one experimental one [A.V. Timofeev, M. Meschke, J.T. Peltonen, T.T. Heikkilä and J.P. Pekola, Phys. Rev. Lett. (2007), in press].