  Studies of energy flow in quantum systems complement the information provided
by common conductance measurements. The quantum limit of heat flow in one
dimensional (1D) ballistic modes was predicted, and experimentally
demonstrated, to have a universal value for bosons, fermions, and fractionally
charged anyons. A fraction of this value is expected in non-abelian states.
Nevertheless, open questions about energy relaxation along the propagation
length in 1D modes remain. Here, we introduce a novel experimental setup that
measures the energy relaxation in chiral 1D modes of the quantum Hall effect
(QHE). Edge modes, emanating from a heated reservoir, are partitioned by a
quantum point contact (QPC) located at their path. The resulting noise allows a
determination of the 'effective temperature' at the location of the QPC. We
found energy relaxation in all the tested QHE states, being integers or
fractional. However, the relaxation was found to be mild in particle-like
states, and prominent in hole-conjugate states.
