Abstract 11 February 2015

Quiet electrons for electron quantum optics: the levitons

D. Christian Glattli, Nanoelectronics group, CEA Saclay, France

Recent advances in quantum conductors have enable the realization of electronic analog of photonic interferometers. Observing electron interference is routine via electrical current measurements where a macroscopic number of electrons flow through the conductor. A full electron quantum optics experiment however requires controlling the current at the single electron level, i.e. the realization of an on-demand single electron sources analogous to single photon source.

How to send a single charge in a conductor? In the past, manipulation of single charges was first done by building ultra-small metallic islands separated from the conductor by a tunnel barrier. Taking benefit of charge and level quantization on the nearly isolated metallic island, a single electron could be emitted in the conductor by a sudden rise of the island potential. However, this approach requires delicate nanofabrication, suffers from quantum jittering making uncertain the electron emission time and from the generation of parasitic electron-hole pair excitations.

A much simpler approach would be to apply a voltage pulse on a contact of the conductor such that the resulting current pulse injects a single charge in the conductor. At first sight, the idea seems too naive to produce something useful. However it appears that this procedure perfectly works [1]. More surprisingly it contains a rich physics: the generation of a new kind of excitation carrying a single particle: a leviton. This approach was already theoretically considered about twenty years ago by L. Levitov and collaborators [2] who found an ingenious way to inject electrons using voltage pulses while producing a minimal excitation, i.e. such that the number of excitations generated is not larger than the number of injected charges.

After a brief introduction to quantum transport and review of the early single electron sources, I will focus on the recent experimental generation of levitons. As an application, I will describe a two-leviton quantum interference experiment, the electrical analog of the Hong Ou Mandel experiment with photons. Finally from quantum tomography measurements [3] an almost complete picture of the Leviton wave-function will be given.

 [1] J. Dubois et al, Nature 502, 659-663 (2013)

[2] Levitov, L. S., Lee, H. & Lesovik,  J. Math. Phys. 37, 4845–4856 (1996) ; Keeling, J., Klich, I. & Levitov, L., Phys. Rev. Lett. 97, 116403 (2006)

[3] T. Jullien et al., Nature 514, 603–607 (2014)

 


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