ABSTRACT We report the measurement of the fourth cumulant of current fluctuations in a tunnel junction under both dc and ac (microwave) excitation. This probes the non-Gaussian character of

photo-assisted shot noise. Our measurement reveals the existence of correlations between noise power measured at two different frequencies, which corresponds to two-mode intensity

correlations in optics. We observe positive correlations, _i.e._ photon bunching, which exist only for certain relations between the excitation frequency and the two detection frequencies,

depending on the dc bias of the sample. SIMILAR CONTENT BEING VIEWED BY OTHERS DETECTION OF SINGLE-MODE THERMAL MICROWAVE PHOTONS USING AN UNDERDAMPED JOSEPHSON JUNCTION Article Open access

particular interest are the deviations from the ubiquitous Gaussian noise, _i.e._ the study of high order cumulants. As a matter of fact, while the only parameter characterizing a Gaussian

distribution, the variance or _second cumulant_ of the fluctuations, contains some information about electron transport, much more could be learned by the statistical study of the

fluctuations beyond their variance. These are characterized by cumulants of order three and higher, which are zero for a Gaussian distribution. For the simplest systems, such as a tunnel

junction between normal metals or a quantum point contact, only the third cumulant has been measured until now3,4,5,6. Higher order cumulants have been experimentally accessible solely in

quantum dots where electrons enter only one by one7,8,9. In all these measurements the system is driven out of equilibrium by a dc voltage bias. Here we address the statistics of

photo-assisted shot noise, _i.e._ current fluctuations in the presence of an ac excitation. While the variance of such fluctuations has been well explored both theoretically10,11,12,13 and

experimentally14,15,16,17,18,19, no experiment has been performed yet that reports the existence of higher order cumulants in such conditions. In the following we present a link between the

measurement of the correlation _G_2 = 〈_P_1_P_2〉 − 〈_P_1〉 〈_P_2〉 between the noise powers _P_1 and _P_2 at two different frequencies in the GHz range, _f_1 and _f_2. The source of shot noise

is a tunnel junction that is dc biased and excited at frequency _f_0. Since power fluctuations of Gaussian noise are independent at all frequencies, our measurement probes only the

non-Gaussian part of current fluctuations. This technique has been applied many times to the study of 1/_f_ noise in glassy or disordered materials20,21,22,23 and has been proposed to

measure the fourth cumulant of a quantum point contact without ac excitation24. In optics, _G_2 corresponds to intensity-intensity correlations, a usual probe of the statistical properties

of light25. Here we show that _G_2 gives the fourth cumulant at frequencies (_f_1, _f_2, 0) of photo-assisted shot noise in the tunnel junction. In the optics community, current/voltage

fluctuations, which are simply another point of view of a fluctuating electromagnetic field, are rather thought of as time dependent electric and magnetic fields. Thus, a noisy electronic

device is also a light source and it is natural to apply tools developed in optics to analyze high frequency electronic noise24,26,27. This point of view will also be studied. RESULTS

EXPERIMENTAL PRINCIPLE The experimental setup is depicted on Fig. 1. The sample, a tunnel junction described in the _Methods_ section, is voltage biased by a dc source and connected to

microwave signal generators below 4 GHz and above 8 GHz while the noise generated by the junction at point _A_ is amplified by a cryogenic amplifier in the 4–8 GHz frequency range. This

setup allows noise to be measured in the 4–8 GHz range while the excitation frequency _f_0 can take any value below 4 GHz or above 8 GHz. This insures that the amplifier never sees the ac

excitation of the sample, which avoids spurious signals due to non-linearities in the amplifier at high excitation power. However, it prevents the use of an excitation frequency in the range

4–8 GHz. The amplified noise is split into two branches: in branch 1 (respectively branch 2) the signal is bandpass filtered around _f_1 = 4.5 GHz with a bandwidth Δ_f_1 = 0.72 GHz (resp.

_f_2 = 7.1 GHz, Δ_f_2 = 0.60 GHz). In each branch a fast power detector (diode symbol on Fig. 1, bandwidth ) measures the “instantaneous” (averaged over a few ns) noise power integrated in

the corresponding bandwidth, _i.e._ with _k_ = 1, 2. The dc voltage at point _B__k_ is thus proportional to the noise spectral density, _S_(_f__k_) = 〈|_i_(_f__k_)|2〉 with _i_(_f_) the

Fourier component of the instantaneous current: . A dc block (capacitor on Fig. 1) removes the dc part of _v__B_ to give . Finally, voltages at points _C_1 and _C_2 are simultaneously

digitized with a 2-channel, 14-bit, 400 MS/s acquisition card and the correlator _G_2 = 〈_δP_1_δP_2〉 is computed in real time by a 12-core parallel computer, as are the autocorrelations of

both channels . THE FOURTH CUMULANT OF NOISE In order to describe and understand the meaning of the observed correlator, let us first express the noise generated by the sample in Fourier

space. We define the power fluctuations _δP__k_(_t_) = _P__k_(_t_) − 〈_P__k_〉 so that _G_2 = 〈_δP_1(_t_)_δP_(2(_t_)〉. The average 〈.〉 is performed over time. Introducing the Fourier

component of the power fluctuations _δP__k_(ε) at frequency ε, one has: . Here ε is a low frequency limited by the output bandwidth of the power detectors. Note that _δP__k_(ε = 0) = 0,

while power fluctuations at finite frequency ε are related to current fluctuations by where _i_(_f_) is the fluctuating current's Fourier component at frequency _f_. This integral spans

over the bandwidth of the bandpass filters, _i.e._ _f__k_ ± Δ_f__k_/2. Thus, _G_2 is proportional to the correlator between currents at four _different_ frequencies which, by definition, is

the time averaged fourth _cumulant_ of current fluctuations taken at frequencies _f_1, _f_2 and ε (with ε → 0 but ε ≠ 0). Noting _i__k_(_t_) the current after bandpass filtering around

±_f__k_, one has , the averaging being performed over the time _t_. Here 〈〈_x_4〉〉 = 〈_x_4〉 − 3 〈_x_2〉2 is the fourth cumulant of the random variable _x_ with 〈_x_〉 = 0. For a Gaussian

distribution, 〈〈_x_4〉〉 = 0, so there is no information in the fourth moment that is not contained in the variance. In contrast, for a non-Gaussian distribution, the fourth moment differs

from 3 〈_x_2〉2, though only very slightly for current fluctuations involving many electrons, so the fourth cumulant is non-zero. FREQUENCY DEPENDENCE The first step in the observation of

_G_2(_V_dc, _V_ac, _f_0) is to determine the excitation frequency for which _G_2 ≠ 0. This is done by measuring _G_2 at fixed bias voltage (_V_dc = 0 or _V_dc = 2.4 mV) and fixed excitation

amplitude (_V_ac = 1.1 mV) while varying the excitation frequency _f_0 from 10 MHz to 3.83 GHz and from 10 GHz to 14 GHz. These results are reported in Fig. 2, where _G_2 has been reduced to

units of K2 as the measured noise spectral density _S_ of a conductor of resistance _R_ is often given in terms of equivalent noise temperature _T_noise = _RS_/2_k__B_. We observe that _G_2

is large at low frequency for both bias voltages. This simply reflects that a slow oscillation of the bias voltage induces a slow modulation of the noise, _i.e._ a slow oscillation of both

_P_1 and _P_2. The response disappears when the modulation frequency exceeds the output bandwidth of the power detectors. At much higher excitation frequencies, _G_2 strongly depends on

_V_dc. For _V_dc = 2.4 mV, _G_2 shows peaks at _f_0 = 2.6 GHz and _f_0 = 11.6 GHz, which correspond to , where _f_1 and _f_2 are the signal observation frequencies. At zero bias, _G_2 peaks

at _f_0 = 1.3 GHz, or _f_−/2. Choosing _f_0 = _f_+/2 was not possible with this experimental setup since it lies in the 4–8 GHz range. To understand why _G_2 is nonzero at high excitation

frequency, let us first consider the correlator 〈_i_(_f_)_i_(_f_′)〉. The latter is non-vanishing only for frequencies such that _f_ + _f_′ = _nf_0 with _n_, an integer. The case _n_ = 0

corresponds to photo-assisted noise whereas _n_ ≠ 0 describes the noise dynamics, characterized by the correlator _X__n_(_f_, _f_0) = 〈_i_(_f_)_i_(_nf_0 − _f_)〉17,28,29. In order to detect

the fourth cumulant and not the fourth moment of current fluctuations, it is crucial that the four frequencies involved in _G_2 (see Eq. 1 where ε ≠ 0) be different so that correlators

〈_i_(_f_)_i_(−_f_)〉 are never involved. Experimentally, the separation of the signal into two branches with non-overlapping bandwidths insures that _f_1 ≠ ± _f_2, while the presence of the

dc blocks, by imposing ε ≠ 0, prevents all other possible occurrences of such correlators. In our experimental setup, relevant frequencies are close to ±_f_1 and ±_f_2, so this condition

becomes _f_1 ± _f_2 = _nf_0, _i.e._ _f_0 = _f_±/_n_. In such cases, the fourth order correlator of Eq. (1) is dominated by the terms . This product is zero unless _f_1 ± _f_2 = _nf_0, as we

observe on Fig. 2. VOLTAGE DEPENDENCE We now consider the variation of _G_2 as a function of the dc voltage for various ac excitation amplitudes at fixed excitation frequency _f_0 =

_f_±/_n_. Data on Fig. 3 correspond to an excitation at _f_0 = _f_+. We observe that _G_2 is maximal at high dc bias and vanishes at _V_dc = 0. We obtained identical results for _f_0 = _f_−

(data not shown). Data on Fig. 4 correspond to _f_0 = _f_−/2. Here _G_2 peaks at 0 dc bias and decays when |_V_dc| increases. Moreover, the maximum of _G_2(_f_0 = _f_±) for a given _V_ac is

an order of magnitude larger than that of _G_2(_f_0 = _f_−/2). The voltage dependence of the signal can be explained by expressing _G_2 in terms of the correlators _X__n_(_f_, _f_0): with .

The exact value of _K_ involves integrals of the gain of the setup over the actual bandwidth of the filters as well as the coupling coefficient between the sample and the detection setup,

which depends on the impedance of the sample. The correlators _X__n_ have been calculated and measured in the quantum regime at very low temperature17,28,29. In the high temperature,

classical regime that corresponds to the present experiment, _X__n_ reduces to: Here _S_0(_V_) = 2 _eGV_ coth(_eV_/2_k__B__T_) is the noise of the junction at zero frequency in the absence

of ac excitation. Eq. 3 is interpreted as follows: in the classical regime, the noise responds instantaneously to the time-dependent voltage _V_(_t_) = _V_dc + _V_ac cos θ with θ =

2_πf_0_t_, so it oscillates at frequency _f_0 and its harmonics. _X__n_ is the amplitude of the n_th_ harmonics. _X__n_ is independent of _f_ and _f_0 as long as _hf_, , so depends only on

|_n_|. For small _V_ac and _f_0 = _f_±, the noise oscillates with an amplitude given by , so computes to zero at _V_dc = 0 and is maximal at large _V_, which corresponds to the shape

observed on Fig. 3. For _f_0 = _f_±/2, _G_2 is given by the amplitude of the noise that oscillates at 2_f_0, which is given by for small _V__ac_. Therefore is maximal at _V_dc = 0 and decays

at finite dc bias, as observed on Fig. 4. Solid lines on Fig. 3 and 4 represent the theoretical predictions of Eqs. (2,3) and agree very well with the measurements. PHOTON BUNCHING Current

fluctuations generated by a tunnel junction are known to be non-Gaussian and thus should exhibit a non-zero fourth cumulant even in the absence of ac excitation30. This contribution,

together with potential environmental effects31,32 are negligible as compared to the signals we report here. For example, at _V__dc_ = 2 mV and _V__ac_ = 0, the correlator would correspond

to _G_2 ~ 10−4 K2. Thus, by adding an ac excitation on the sample we have been able to boost the fourth cumulant by 5 orders of magnitude. Furthermore, our experiment corresponds to

intensity-intensity correlation, which is the usual way used to differentiate classical from quantum light by showing evidence of photon bunching or anti-bunching. More precisely, in order

to make a connection with experiments performed in optics, let us define the dimensionless correlator: which is usually referred to as the same-time two-mode second order correlator of the

electromagnetic field radiated by the junction. The variations of _g_2 as a function of _V_dc are depicted on Fig. 5 for fixed _V_ac = 1.0 mV for both _f_0 = _f_+ (red triangles) and _f_0 =

_f_−/2 (green circles). It is clear from these data that we always observe a positive correlation between the power fluctuations, _i.e._ photon bunching (_g_2 > 1). Each acquisition

performed by the digitizer (integrated over τ = 2.5 ns) corresponds to an averaged number of 〈_n_2〉 = _P_2τ/_hf_2 ~ 21 photons at 7.2 GHz emitted by the sample at _V_dc = _V_ac = 1 mV and

_f_0 = _f_+, plus ~40 photons from the amplifier. Thus our experiment does not measure correlations at the single photon level, but is not very far from that limit, which can be reached by

lowering the temperature and the ac power. DISCUSSION It follows from the observed behaviour that by choosing the excitation frequency, dc bias and ac excitation, we can control how

non-Gaussian the shot noise of the junction can be. The level of non-Gaussianity of the signal is characterised here by the fourth cumulant, which is directly linked to the measured

correlator. It should be noted that the power detector, which measures the square of the electric field, cannot differentiate absorption from emission of photons by the sample. This has to

be taken into account when comparing the data with theories such as24,26,27 which consider photon detectors. In particular, the correlations between photon detectors will involve other

current correlators33. Whereas _G_2 at excitation frequency _f_0 = _f_1 + _f_2 corresponds to absorption of one photon of frequency _f_0 and emission of two correlated photons, one at _f_1

and one at _f_2, the case of excitation at frequency _f_0 = _f_2 − _f_1 corresponds to two photons being absorbed, one at _f_0 and one at _f_1 while one photon at frequency _f_2 is emitted.

We indeed observe no difference in _G_2 for _f_0 = _f_+ and _f_0 = _f_−. The tunnel junction behaves as a source of white noise whose amplitude is instantaneously modulated by the bias

voltage. This description holds only because the temperature is large in the present experiment. At very low temperature, the noise can no longer be considered as white and no longer

responds adiabatically to an ac excitation, so Eq.(3) will no longer be valid. In particular, _X__n_ depends on _f_ and _f_0, so that excitations at _f_1 + _f_2 or _f_1 − _f_2 will no longer

correspond to the same _G_2. Still the present analysis and in particular the link between _G_2 and _X__n_ given by Eq.(2), will remain valid. Our measurements open the way to the study of

the fourth cumulant of current fluctuations in the quantum regime at very low temperature, where the same setup can be used to detect correlations at the single photon level. METHODS SAMPLE

We have chosen to perform the measurement on the simplest system that exhibits well understood shot noise, the tunnel junction. The sample is a ~1 μm × 15 μm Al/Al oxide/Al tunnel junction

made by photolithography, similar to that used for noise thermometry34, cooled at _T_ = 3.0 K so the aluminum remains a normal metal. The resistance of the junction at that temperature, _R_

= 22 Ω, is close enough to the 50 Ω impedance of the microwave circuitry to ensure a good coupling. The capacitance of the junction corresponds to an _RC_ frequency cutoff of ~6 GHz, so it

influences the amplitude of the noise we measure and the amplitude of the ac excitation experienced by the junction. Both effects are calibrated out as explained below. CALIBRATION In order

to have a quantitative measurement of _G_2, it is necessary to calibrate the ac excitation voltage reaching the sample and the overall gain of the detection. The calibration of the ac

voltage across the sample is performed by measuring the usual photo-assisted noise, _i.e. S_ vs _V_dc, in the presence of a microwave excitation for various excitation voltages10,14. The

temperature is large enough () to approximate the noise measured in either branch by its value at zero frequency. In the absence of ac excitation, the noise spectral density is given by

_S_0(_V_dc) = _eGV_dc coth(_eV_dc/2_k__B__T_) with _G_ = 1/_R_, the sample's conductance. Since the excitation frequency _f_0 is always such that , the photo-assisted noise can be

approximated by its time-average value as if the junction were responding instantaneously to the time-dependent voltage. To calibrate the gain of the setup, we consider the single channel

autocorrelations . Those are also related to fourth order current correlators 〈_i_ (_f_) _i_ (ε − _f_) _i_ (_f_′) _i_ (−ε − _f_′)〉. However, here _f_ and _f_′ belong to the same frequency

band, so the correlator is dominated by terms _f_ = −_f_′ and . The fourth cumulant _G_2 is only a very small correction to this. Thus, power correlations within the same frequency band are

totally dominated by Gaussian fluctuations, as in35. Note that since the amplifier noise dominates 〈_P__k_〉, it also dominates , but only the fourth cumulant of the amplifier's noise

contributes to _G_2 (here a very small contribution). REFERENCES * Blanter, Y. M. & Büttiker, M. Shot noise in mesoscopic conductors. Phys. Rep. 336, 1–166 (2000). Article  CAS  ADS 

Google Scholar  * Nazarov, Y. V. & Blanter, Y. M. Quantum Noise In Mesoscopic Physics. Nato Science Series vol. II/97, Kluwer Academic Publishers (2009). Google Scholar  * Reulet, B.,

Senzier, J. & Prober, D. E. Environmental effects in the third moment of voltage fluctuations in a tunnel junction. Phys. Rev. Lett. 91, 196601 (2003). Article  CAS  ADS  Google Scholar

  * Bomze, Y., Gershon, G., Shovkun, D., Levitov, L. S. & Reznikov, M. Measurement of counting statistics of electron transport in a tunnel junction. Phys. Rev. Lett. 95, 176601 (2005).

Article  ADS  Google Scholar  * Gershon, G., Bomze, Y., Sukhorukov, E. V. & Reznikov, M. Detection of non-gaussian fluctuations in a quantum point contact. Phys. Rev. Lett. 101, 016803

(2008). Article  CAS  ADS  Google Scholar  * Gabelli, J. & Reulet, B. High frequency dynamics and the third cumulant of quantum noise. J. Stat. Mech. P01049 (2009). * Gustavsson, S. et

al. Counting statistics of single electron transport in a quantum dot. Phys. Rev. Lett. 96, 076605 (2006). Article  CAS  ADS  Google Scholar  * Gustavsson, S. et al. Measurements of

higher-order noise correlations in a quantum dot with a finite bandwidth detector. Phys. Rev. B 75, 075314 (2007). Article  ADS  Google Scholar  * Flindt, C. et al. Universal oscillations in

counting statistics. Proc. Natl. Acad. Sci. USA 106, 10116 (2009). Article  CAS  ADS  Google Scholar  * Lesovik, G. B. & Levitov, L. S. Noise in an ac biased junction: nonstationary

Aharonov-Bohm effect. Phys. Rev. Lett. 72, 538 (1994). Article  CAS  ADS  Google Scholar  * Vanevic, M., Nazarov, Y. V. & Belzig, W. Elementary events of electron transfer in a

voltage-driven quantum point contact. Phys. Rev. Lett. 99, 076601 (2007). Article  ADS  Google Scholar  * Vanevic, M., Nazarov, Y. V. & Belzig, W. Elementary charge-transfer processes in

mesoscopic conductors. Phys. Rev. B 78, 245308 (2008). Article  ADS  Google Scholar  * Vanevic, M. & Belzig, W. Control of electron-hole pair generation by biharmonic voltage drive of a

quantum point contact. Phys. Rev. B 86, 241306 (2012). Article  ADS  Google Scholar  * Schoelkopf, R. J., Kozhevnikov, A. A. & Prober, D. E. Observation of “photon-assisted” shot noise

in a phase-coherent conductor. Phys. Rev. Lett. 80, 2437 (1998). Article  CAS  ADS  Google Scholar  * Kozhevnikov, A. A., Schoelkopf, R. J. & Prober, D. E. Observation of Photon-Assisted

Noise in a Diffusive Normal Metal-Superconductor Junction. Phys. Rev. Lett. 84, 3398 (2000). Article  CAS  ADS  Google Scholar  * Reydellet, L.-H., Roche, P., Glattli, D. C., Etienne, B.

& Jin, Y. Quantum partition noise of photon-created electron-hole Pairs. Phys. Rev. Lett. 90, 176803 (2003). Article  ADS  Google Scholar  * Gabelli, J. & Reulet, B. Dynamics of

quantum noise in a tunnel junction under ac excitation. Phys. Rev. Lett. 100, 026601 (2008). Article  CAS  ADS  Google Scholar  * Gabelli, J. & Reulet, B. Shaping a time-dependent

excitation to minimize the shot noise in a tunnel junction. Phys. Rev. B 87, 075403 (2013). Article  ADS  Google Scholar  * Gasse, G., Spietz, L., Lupien, C. & Reulet, B. Observation of

quantum oscillations in the photo-assisted shot noise of a tunnel junction. arXiv1304.6951 (unpublished). * Restle, P. J., Weissman, M. B. & Black, R. D. Tests of Gaussian statistical

properties of 1/f noise. J. Appl. Phys. 54, 5844 (1983). Article  CAS  ADS  Google Scholar  * Weissman, M. B. 1/f noise and other slow, nonexponential kinetics in condensed matter. Rev. Mod.

Phys. 60, 537 (1988). Article  CAS  ADS  Google Scholar  * Parman, C. E., Israeloff, N. E. & Kakalios, J. Conductance-noise power fluctuations in hydrogenated amorphous silicon. Phys.

Rev. Lett. 69, 1097 (1992). Article  CAS  ADS  Google Scholar  * Weissman, M. B. What is a spin glass? A glimpse via mesoscopic noise. Rev. Mod. Phys. 65, 829 (1993). Article  CAS  ADS 

Google Scholar  * Lebedev, A. V., Lesovik, G. B. & Blatter, G. Statistics of radiation emitted from a quantum point contact. Phys. Rev. B 81, 155421 (2010). Article  ADS  Google Scholar

  * Loudon, R. The Quantum Theory of Light. Oxford University Press, Third edition (2000). * Beenakker, C. W. J. & Schomerus, H. Counting statistics of photons produced by electronic

shot noise. Phys. Rev. Lett. 86, 700 (2001). Article  CAS  ADS  Google Scholar  * Beenakker, C. W. J. & Schomerus, H. Antibunched photons emitted by a quantum point contact out of

equilibrium. Phys. Rev. Lett. 93, 096801 (2004). Article  CAS  ADS  Google Scholar  * Gabelli, J. & Reulet, B. The noise susceptibility of a photo-excited coherent conductor.

arXiv:0801.1432 (unpublished). * Gabelli, J. & Reulet, B. The noise susceptibility of a coherent conductor. Proceedings of SPIE, Fluctuations and Noise in Materials, 6600 (2007). *

Levitov, L. S., Lee, H. W. & Lesovik, G. B. Electron counting statistics and coherent states of electric current. J. Math. Phys. 37, 4845–4866 (1996). Article  ADS  MathSciNet  Google

Scholar  * Beenakker, C. W. J., Kindermann, M. & Nazarov, Y. V. Temperature-dependent third cumulant of tunneling noise. Phys. Rev. Lett. 90, 176802 (2003). Article  CAS  ADS  Google

Scholar  * Kindermann, M., Nazarov, Y. V. & Beenakker, C. W. J. Feedback of the electromagnetic environment on current and voltage fluctuations out of equilibrium. Phys. Rev. B 69,

035336 (2004). Article  ADS  Google Scholar  * Bednorz, A. & Belzig, W. Models of mesoscopic time-resolved current detection. Phys. Rev. B 81, 125112 (2010). Article  ADS  Google Scholar

  * Spietz, L., Lehnert, K. W., Siddiqi, I. & Schoelkopf, R. J. Primary electronic thermometry using the shot noise of a tunnel junction. Science 300, 1929–1932 (2003). Article  CAS  ADS

  Google Scholar  * Zakka-Bajjani, E. et al. Experimental determination of the statistics of photons emitted by a tunnel junction. Phys. Rev. Lett. 104, 206802 (2010). Article  ADS  Google

Scholar  Download references ACKNOWLEDGEMENTS We acknowledge fruitful discussions with A. Bednorz, W. Belzig, M. Devoret and J. Gabelli and technical help from G. Laliberté. This work was

supported by the Canada Excellence Research Chairs program, the NSERC, the MDEIE, the FRQNT via the INTRIQ and the Canada Foundation for Innovation. AUTHOR INFORMATION AUTHORS AND

AFFILIATIONS * Département de Physique, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada Jean-Charles Forgues, Fatou Bintou Sane, Christian Lupien & Bertrand Reulet *

Département de Génie électrique, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada Simon Blanchard * National Institute of Standards and Technology, Boulder, Colorado, 80305, USA

Lafe Spietz Authors * Jean-Charles Forgues View author publications You can also search for this author inPubMed Google Scholar * Fatou Bintou Sane View author publications You can also

search for this author inPubMed Google Scholar * Simon Blanchard View author publications You can also search for this author inPubMed Google Scholar * Lafe Spietz View author publications

You can also search for this author inPubMed Google Scholar * Christian Lupien View author publications You can also search for this author inPubMed Google Scholar * Bertrand Reulet View

author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS J.-C.F. and F.B.S. performed the measurements and data analysis, S.B. designed and implemented

the real-time digital correlator, L.S. fabricated the samples, C.L. designed and programmed the control of the experiments. B.R. designed the experiment and performed the theory. B.R. and

C.L. supervised the measurements. The article was mainly written by J.-C.F. and B.R. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing financial interests. RIGHTS AND

PERMISSIONS This work is licensed under a Creative Commons Attribution-NonCommercial-ShareALike 3.0 Unported License. To view a copy of this license, visit

http://creativecommons.org/licenses/by-nc-sa/3.0/ Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Forgues, JC., Sane, F., Blanchard, S. _et al._ Noise Intensity-Intensity

Correlations and the Fourth Cumulant of Photo-assisted Shot Noise. _Sci Rep_ 3, 2869 (2013). https://doi.org/10.1038/srep02869 Download citation * Received: 22 July 2013 * Accepted: 19

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