  Electrical conductance measurements have limited scope in identifying Andreev
edge states (AESs), which form the basis for realizing various topological
excitations in quantum Hall (QH) - superconductor (SC) junctions. To
unambiguously detect AESs, we measure shot noise along with electrical
conductance in a graphene based QH-SC junction at integer filling nu=2.
Remarkably, we find that the Fano factor of shot noise approaches half when the
bias energy is less than the superconducting gap, whereas it is close to zero
above the superconducting gap. This is striking, given that, at the same time,
the electrical conductance remains quantized at 2e^2/h within and above the
superconducting gap. A quantized conductance is expected to produce zero shot
noise due to its dissipationless flow. However, at a QH-SC interface, AESs
carry the current in the zero-bias limit and an equal mixing of electron and
hole like states produces half of the Poissonian shot noise with quantized
conductance. The observed results are in accord with our detailed theoretical
calculations of electrical conductance and shot noise based on non-equilibrium
Green's function method in the presence of disorder. Our results pave the way
in using shot noise as a detection tool in the search of exotic topological
excitations in QH-SC hybrids.
