Irreversibility on the Level of Single-Electron Tunneling
  We present a low-temperature experimental test of the fluctuation theorem for electron transport through a double quantum dot. The rare entropy-consuming system trajectories are detected in the form of single charges flowing against the source-drain bias by using time-resolved charge detection with a quantum point contact. We find that these trajectories appear with a frequency that agrees with the theoretical predictions even under strong nonequilibrium conditions, when the finite bandwidth of the charge detection is taken into account. 
B. K\"ung, C. R\"ossler, M. Beck, M. Marthaler, D. S. Golubev, Y.   Utsumi, T. Ihn, and K. Ensslin
cond-mat.mes-hall