Talk given by

Dr. Preden Roulleau
CEA, IRAMIS

Saclay, France

Abstract:

The on-demand generation of pure quantum excitations is important for the operation of 
quantum systems, but it is particularly difficult for a system of fermions. This is because any 
perturbation affects all states below the Fermi energy, resulting in a complex superposition of 
particle and hole excitations. However, it was predicted nearly 20 years ago that a Lorentzian 
time-dependent potential with quantized flux generates a minimal excitation with only one 
particle and no hole. 

Here we report that such quasiparticles (hereafter termed levitons) can be generated on demand
in a conductor by applying voltage pulses to a contact. Partitioning the excitations with an 
electronic beam splitter generates a current noise that we use to measure their number. 
Minimal-excitation states are observed for Lorentzian pulses, whereas for other pulse shapes 
there are significant contributions from holes. Further identification of levitons is provided in the 
energy domain with shot-noise spectroscopy, and in the time domain with electronic 
Hong–Ou–Mandel noise correlations. The latter, obtained by colliding synchronized levitons on a 
beam splitter, exemplifies the potential use of levitons for quantum information: using linear 
electron quantum optics in ballistic conductors, it is possible to imagine flying-qubit operation in 
which the Fermi statistics are exploited to entangle synchronized electrons emitted by distinct 
sources. We will show that using Levitons, we could realize for the first time the tomography 
of an itinerant electron.

Minimal-excitation states for electron quantum optics using levitons,  
J. Dubois,  T. Jullien,  F. Portier,  P. Roche, A. Cavanna, Y. Jin, W. Wegscheider,  P. Roulleau,  
& D. C. Glattli, Nature 502, 659-663 (2013)
Quantum tomography of an electron, 
T. Jullien, P. Roulleau, B. Roche, A. Cavanna, Y. Jin & D.C. Glattli, Nature 514, 603-607 (2014)