Dynamics of Quantum Noise in a Tunnel Junction under ac Excitation

TL;DR

This paper presents the first experimental study of how shot noise in a quantum tunnel junction responds dynamically to high-frequency ac excitation, revealing non-adiabatic behavior consistent with theoretical predictions.

Contribution

It provides the first measurement of the dynamical response of shot noise at high frequencies in the quantum regime, confirming theoretical models with experimental data.

Findings

Noise responds in phase with ac excitation

Response is non-adiabatic

Results agree with theoretical current-current correlator prediction

Abstract

We report the first measurement of the \emph{dynamical response} of shot noise (measured at frequency $\omega$) of a tunnel junction to an ac excitation at frequency $\omega_0$. The experiment is performed in the quantum regime, $\hbar\omega\sim\hbar\omega_0\gg k_BT$ at very low temperature T=35mK and high frequency $\omega_0/2\pi=6.2$ 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.