  The quantum of heat conductance of ballistic one-dimensional (1D) channels,
being gQ=k0T with k0=pi^2*2kB^2/3h (T - temperature, kB - Boltzmann's constant,
h - Planck's constant), is an important fundamental constant. While the
quantization of the electrical conductance of 1D ballistic conductors has long
been experimentally established, a demonstration of the quantization of thermal
conductance proved to be much harder. It has already been accomplished for
weakly interacting systems of phonons, photons, and electronic Fermi-liquids.
Theoretically, however, the quantization must also hold in strongly interacting
systems, such as the Fractional Quantum Hall effect (FQHE), where electrons
fractionalize into anyons and chargeless quasiparticles such as neutral
Majorana fermions. Since the bulk in the FQHE is incompressible, it is not
expected to contribute significantly to the heat conductance, which is
determined by chiral 1D edge modes. The thermal conductance reflects
topological properties of the FQH electronic systems to which the electrical
conductance gives no access. Here, we present results of extensive measurements
of the heat conductance in 'particle-like' (Laughlin's) and 'hole-like'
fractional states. We verify the universal value of the quantum of thermal
conductance of the charged fractional modes as well as for chargeless neutral
modes. We also prove the validity of the theoretical predictions for the more
complex (and less studied) 'hole-like' states. Heat transport measurements open
a door to ample information, not easily accessible by conductance measurements.
