Measuring the distribution of current fluctuations through a Josephson junction with very short current pulses

¹  NEST CNR-INFM and Scuola Normale Superiore - I-56126 Pisa, Italy, EU
²  University Joseph Fourier and LPMMC-CNRS - B.P. 166, 25 Avenue des Martyrs, 38042 Grenoble-cedex 09, France, EU

Corresponding author: f.taddei@sns.it

Received: 5 February 2008
Accepted: 26 June 2008

Abstract

We propose to probe the distribution of current fluctuations by means of the escape probability histogram of a Josephson junction (JJ), obtained using very short bias current pulses in the adiabatic regime, where the low-frequency component of the current fluctuations plays a crucial role. We analyze the effect of the third cumulant on the histogram in the small skewness limit, and address two concrete examples assuming realistic parameters for the JJ. In the first one we study the effects due to fluctuations produced by a tunnel junction, finding that the signature of higher cumulants can be detected by taking the derivative of the escape probability with respect to current. In such a realistic situation, though, the determination of the whole distribution of current fluctuations requires an amplification of the cumulants. As a second example we consider magnetic flux fluctuations acting on a SQUID produced by a random telegraph source of noise.