Noise Intensity-Intensity Correlations and the Fourth Cumulant of Current Fluctuations

摘要

We report measurements of the correlation between intensities of noise atdifferent frequencies on a tunnel junction under ac excitation, whichcorresponds to two-mode intensity correlations in optics. We observe positivecorrelation, \emph{i.e.} photon bunching, which exist only for certainrelations between the excitation frequency and the two detection frequencies,depending on the dc bias of the sample. We demonstrate that these correlationsare proportional to the fourth cumulant of current fluctuations.