  Mesoscopic systems -- small electric circuits working in quantum regime --
offer us a unique experimental stage to explorer quantum transport in a tunable
and precise way. The purpose of this Review is to show how they can contribute
to statistical physics. We introduce the significance of fluctuation, or
equivalently noise, as noise measurement enables us to address the fundamental
aspects of a physical system. The significance of the fluctuation theorem (FT)
in statistical physics is noted. We explain what information can be deduced
from the current noise measurement in mesoscopic systems. As an important
application of the noise measurement to statistical physics, we describe our
experimental work on the current and current noise in an electron
interferometer, which is the first experimental test of FT in quantum regime.
Our attempt will shed new light in the research field of mesoscopic quantum
statistical physics.
