  Fluctuations of the current through a tunnel junction are measured using a
Josephson junction. The current noise adds to the bias current of the Josephson
junction and affects its switching out of the supercurrent branch. The
experiment is carried out in a regime where switching is determined by thermal
activation. The variance of the noise results in an elevated effective
temperature, whereas the third cumulant, related to its asymmetric character,
leads to a difference in the switching rates observed for opposite signs of the
current through the tunnel junction. Measurements are compared quantitatively
with recent theoretical predictions.
