Klaus Ensslin, Swiss Federal Institute of Technology, Zurich
Abstract
Electron counting in transport through semiconductor quantum dots has been established using a quantum point contact as a strongly coupled detector. This way very sensitive measurements of the current (electrons per second), shot noise and higher temporal correlations in the current as well as single-electron interference have been demonstrated on a chip.
The second law of thermodynamics states that a macroscopic system out of thermal equilibrium will irreversibly move toward equilibrium driven by a steady increase of its entropy. This macroscopic irreversibility occurs despite the time-reversal symmetry of the underlying microscopic equations of motion. This phenomenon is described by the fluctuation theorem. We experimentally test the fluctuation theorem in single-electron tunneling at low temperatures by monitoring the charge state of two QDs that are coupled both in series and to source and drain electrodes. This allows us to measure the direction-resolved charge flow through this device and consequently the current probability distribution.