  A chaotic light source is characterized by the fact that many independent
emitters radiate photons with a random optical phase. This is similar compared
to a tunnel junction where many independent channels are able to emit photons
due to a coupling to an electromagnetic environment. However, in a recent
experiment it has been observed that a tunnel junction can deviate from the
expectation of chaotic light and is able to emit strongly correlated,
superbunched photons. Motivated by this, we study the correlation of the
radiation and show that the superbunching originates from the emission of
multiple photons which is possible due to the quantization of charge.
