  Photons are emitted or absorbed by a nano-circuit under both equilibrium and
non-equilibrium situations. Here, we focus on the non-equilibrium situation
arising due to a temperature difference between the leads of a quantum point
contact, and study the finite frequency (colored) noise. We explore this
delta-$T$ noise in the finite frequency regime for two systems: conventional
conductors described by Fermi liquid scattering theory and the fractional
quantum Hall system at Laughlin filling fractions, described by the chiral
Luttinger liquid formalism. We study the emission noise, its expansion in the
temperature difference (focusing on the quadratic component) as well as the
excess emission noise defined with respect to a properly chosen equilibrium
situation. The behavior of these quantities are markedly different for the
fractional quantum Hall system compared to Fermi liquids, signalling the role
of strong correlations. We briefly treat the strong backscattering regime of
the fractional quantum Hall liquid, where a behavior closer to the Fermi liquid
case is observed.
