A very recent article [(1) E. Zakka-Bajjani et al., PRL104, 206802 (2010)] has addressed the problem of how the statistics of electrons crossing a quantum conductor influences that of the photons they emit. It is however not clear that the detection
used in [1] is sensitive to emitted photons and not to the overall electromagnetic fluctuations, which include vacuum fluctuations. We show that the proof in [1] that non-symmetrized noise is detected is erroneous: supposing that the detection simply takes the square of the voltage, i.e. is sensitive to vacuum fluctuations, leads to identical results. We demonstrate that all the results can be explained in terms of usual gaussian voltage fluctuations instead of photon statistics. Finally, it is found in [1] that the photon noise is gaussian for a tunnel junction, for which the electron counting statistics is poissonian. We show that this result is beyond the experimental sensitivity by at least one order of magnitude, and thus is also incorrect.
We report the first experimental data of the third moment of current fluctuations in a tunnel junction. We show that both in the classical and quantum regimes (low or high frequency as compared to voltage), it is given by $S_{I^3}=e^2I$. We discuss environmental effects in both regimes.
We use microwave excitation to elucidate the dynamics of long superconductor / normal metal / superconductor Josephson junctions. By varying the excitation frequency in the range 10 MHz - 40 GHz, we observe that the critical and retrapping currents,
deduced from the dc voltage vs. dc current characteristics of the junction, are set by two different time scales. The critical current increases when the ac frequency is larger than the inverse diffusion time in the normal metal, whereas the retrapping current is strongly modified when the excitation frequency is above the electron-phonon rate in the normal metal. Therefore the critical and retrapping currents are associated with elastic and inelastic scattering, respectively.
We report the first measurement of high order cumulants of the current fluctuations in an avalanche diode run through by a stationary dc current. Such a system is archetypic of devices in which transport is governed by a collective mechanism, here ch
arge multiplication by avalanche. We have measured the first 5 cumulants of the probability distribution of the current fluctuations. We show that the charge multiplication factor is distributed according to a power law that is different from that of the usual avalanche below breakdown, when avalanches are well separated.
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, $hbaromegasimhbaromega_0
gg k_BT$ at very low temperature T=35mK and high frequency $omega_0/2pi=6.2$ 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.
