  Fractional charge and statistics are hallmarks of low-dimensional interacting
systems such as fractional quantum Hall (QH) systems. Integer QH systems are
regarded noninteracting, yet they can have fractional charge excitations when
they couple to another interacting system or time-dependent voltages. Here, we
notice Abelian fractional mutual statistics between such a fractional
excitation and an electron, and propose a setup for detection of the
statistics, in which a fractional excitation is generated at a source and
injected to a Mach-Zehnder interferometer (MZI) in the integer QH regime. In a
parameter regime, the dominant interference process involves braiding, via
double exchange, between an electron excited at an MZI beam splitter and the
fractional excitation. The braiding results in the interference phase shift by
the phase angle of the mutual statistics. This proposal for directly observing
the fractional mutual statistics is within experimental reach.
