  Electrons living in a two-dimensional world under a strong magnetic field -
the so-called fractional quantum Hall effect (FQHE) - often manifest themselves
as fractionally charged quasiparticles (anyons). Moreover, being under special
conditions they are expected to be immune to the environment, thus may serve as
building blocks for future quantum computers. Interference of such anyons is
the very first step towards understanding their anyonic statistics. However,
the complex edge-modes structure of the fractional quantum Hall states,
combined with upstream neutral modes, have been suspected to prevent an
observation of the much sought after interference of anyons. Here, we report of
finding a direct correlation between the appearance of neutral modes and the
gradual disappearance of interference in a Mach-Zehnder interferometer (MZI),
as the bulk filling factor is lowered towards Landau filling {\nu}_B =1;
followed by a complete interference quench at {\nu}_B=1. Specifically, the
interference was found to start diminishing at {\nu}_B~1.5 with a growing
upstream neutral mode, which was detected by a born upstream shot noise in the
input quantum point contact (QPC) to the MZI. Moreover, at the same time a
{\nu}_QPC =1/3 conductance plateau, carrying shot-noise, appeared in the
transmission of the QPC - persisting until bulk filling {\nu}_B =1/2. We
identified this conductance plateau to result from edge reconstruction, which
leads to an upstream neutral mode. Here, we also show that even the
particle-like quasiparticles are accompanied by upstream neutral modes,
therefore suppressing interference in the FQHE regime.
