Counting Statistics of Photons Produced by Electronic Shot Noise

A theory is presented for the photodetection statistics of radiation produced by current fluctuations in a phase-coherent conductor. Deviations are found from the Poisson statistics that would result from a classical current. For detection in a narrow frequency interval δω, the photocount distribution has the negative-binomial form of blackbody radiation if eδω is less than the mean current I¯ in the conductor. When electronic localization sets in, I¯ drops below eδω and a different type of super-Poissonian photon statistics results.