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Abstract: The measurement of higher order cumulants of the current noise generated by anonlinear mesoscopic conductor using a Josephson junction as on-chip detectoris investigated theoretically. The paper addresses the regime where the noiseof the mesoscopic conductor initiates activated escape of the Josephsondetector out of the zero-voltage state, which can be observed as a voltagerise. It is shown that the deviations from Johnson-Nyquist noise can mostly beaccounted for by an effective temperature which depends on the second noisecumulant of the conductor. The deviations from Gaussian statistics lead torather weak effects and essentially only the third cumulant can be measuredexploiting the dependence of the corrections to the rate of escape from thezero-voltage state on the direction of the bias current. These correctionsvanish as the bias current approaches the critical current. The theory is basedon a description of irreversible processes and fluctuations in terms of statevariables and conjugate forces. This approach, going back to work by Onsagerand Machlup, is extended to account for non-Gaussian noise, and it is shownthat the thermodynamically conjugate force to the electric charge plays a rolesimilar to the counting field introduced in more recent approaches to describenon-Gaussian noise statistics. The theory allows to obtain asymptotically exactresults for the rate of escape in the weak noise limit for all values of thedamping strength of the Josephson detector. Also the feedback of the detectoron the noise generating conductor is fully taken into account by treating bothcoupled mesoscopic devices on an equal footing.

Autor: Hermann Grabert


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