  Mesoscopic systems provide us a unique experimental stage to address
non-equilibrium quantum statistical physics. By using a simple tunneling model,
we describe the electron exchange process via a quantum coherent conductor
between two reservoirs, which yields the fluctuation theorem (FT) in mesoscopic
transport. We experimentally show that such a treatment is semi-quantitatively
validated in the current and noise measurement in an Aharonov-Bohm ring. The
experimental proof of the microreversibility assumed in the derivation of FT is
presented.
