Jeudi 14 juin 2012 à 16h30
Salle 234, Ecole de Physique

On-chip photon-assisted detection of the noise of a quantum point contact

Christian Glattli, CEA-Saclay, Paris, France

We describe the first experimental realization of on-chip detection of the noise of a Quantum Point Contact (QPC) (emitter) using an additional capacitively-coupled QPC (detector). The detection is based on the following mechanism: when a QPC is submitted to a time dependent drain-source voltage, electron-hole pairs are generated. Their partitioning at the QPC generates a current noise called photon-assisted shot noise (PASN). Alternatively to shot noise, electron-hole pairs also generate a photon-current. Here, the QPC emitter is dc biased and emits a wide band quantum shot noise proportional to $D^E( 1-D^E )$ where $D^E$ is the transmission of the emitter. Because of the capacitive coupling, this will generate electron-hole pairs on the QPC detector. The induced photon-current is also expected to be proportional to $D^D (1- D^D )$ where $D^D$ is the transmission of the detector. We present photon-current measurements, and observe the expected dependence in $D^D (1-D^D ) D^E (1-D^E )$. This new way of detection, detecting noise with noise, may find fundamental applications in electronic quantum physics.