Mercredi 17 octobre 2012 à 10h15
Salle 234, Ecole de Physique

From single electron partitioning to the single electron collider trap

Gwendal Fève, ENS Paris

The ballistic propagation of electronic waves in the quantum Hall edge channels of a 2DEG bears strong analogies with photon optics. Ballistic and one-dimensional propagation are ensured by the chiral quantum Hall edge states and electronic beam splitters can be implemented using quantum point contacts. These analogies have inspired a whole set of experiments, including the realization of electronic Mach-Zehnder [1] and Hanbury-Brown & Twiss [2] interferometers. I will present two optics-like experiments performed at the single electron scale in the Hanbury-Brown geometry. In the first experiment [3], single elementary electronic excitations are emitted in one input only, and partitioned on the electronic beam-splitter. We show that the measurement of the output currents correlations in the HBT geometry provides a direct counting, at the single charge level, of the elementary excitations (electron/hole pairs) generated by the emitter at each cycle. We observe the antibunching of low energy excitations emitted by the source with thermal excitations of the Fermi sea already present in the input leads of the splitter, which suppresses their contribution to the partition noise. This effect can be used to probe the energy distribution of the emitted wave-packets which can be tuned by varying the emitter parameters. In the second experiment, two single electronic excitations emitted on demand at each input collide on the splitter [4]. If electrons are emitted in the same quantum state, a reduction of the output correlation is observed as indistinguishable fermions antibunch. By delaying the emission times, the full classical partitioning can be recovered [4,5], reproducing the Hong-Ou-Mandel dip [6] of the seminal optical experiment, with approximately a fifty percent visibility. The size of the dip can be controlled by varying the temporal width of the electronic wavepackets. [1] Ji et al., Nature 422, 415 (2003) [2] Henny et al., Science 284, 296 (1999) [3] Bocquillon et al., Physical Review Letters 108, 196803 (2012) [4] Ol'khovskaya et al., Physical Review Letters 101, 166802 (2008) [5] T. Jonckheere et al., Phys. Rev. B 86, 125425 (2012) [6] C. K. Hong et al., Physical Review Letters 59, 2044 (1987)