We show that, in optical pump-probe experiments on bulk samples, thestatistical distribution of the intensity of ultrashort light pulses after theinteraction with a nonequilibrium complex material can be used to measure thetime-dependent noise of the current in the system. We illustrate the generalarguments for a photo-excited Peierls material. The transient noisespectroscopy allows to measure to what extent electronic degrees of freedomdynamically obey the fluctuation-dissipation theorem, and how well theythermalize during the coherent lattice vibrations. The proposed statisticalmeasurement developed here provides a new general framework to retrievedynamical information on the excited distributions in nonequilibriumexperiments which could be extended to other degrees of freedom of magnetic orvibrational origin.
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