Dynamics of Quantum Noise in a Tunnel Junction under ac Excitation

Abstract

We report the first measurement of the \emph{dynamical response} of shot noise (measured at frequency $ω$) of a tunnel junction to an ac excitation at frequency $ω_0$. The experiment is performed in the quantum regime, $\hbarω\sim\hbarω_0\gg k_BT$ at very low temperature T=35mK and high frequency $ω_0/2π=6.2$ GHz. We observe that the noise responds in phase with the excitation, but not adiabatically. The results are in very good agreement with a prediction based on a new current-current correlator.

Theory removed. More experimental details. One extra figure