Quantum guide for electrons
An X researcher is involved in producing the first electron guide in graphene. As an optical fiber, it preserving their quantum character. This new electronic optics tool could be integrated with future quantum technologies and is published in Physical Review Letters the November 22, 2019.
Electron Guidance in Graphene: Artistic depiction by Austin Cheng, Jane Cheng, Julia Mok and Jonathan van der Stel.
Electron guiding has long existed: in a copper wire, by applying a potential difference, it is possible to circulate electrons thus creating an electric current. Nevertheless, this guidance is disordered and involves many interacting electrons. Thanks to the work initiated by Jean-Damien Pillet, a researcher at the Irradiated Solids Laboratory*, it is now possible to circulate electrons in a single-mode guide that preserves their wave character and their quantum characteristics. This research is published in the prestigious journal Physical Review Letters on November 22, 2019.
A technical feat
To product this guide, Austin Cheng, PhD student at Harvard under the direction of Philip Kim and Jean-Damien Pillet, used a carbon nanotube placed near a graphene surface (see illustration above). These two elements are not in contact and a voltage is applied in the nanowire to induce an electrostatic potential in graphene. This potential well, illustrated in the image by a curvature of graphene (in fact graphene remains plane) will guide the electrons which are confined under the nanowire as are photons in an optical fiber or skaters in a half- pipe.
From a technical point of view, this technological solution allows to have monomodal guidance: that is to say that only one "path" is possible for the electrons and they do not interact with electrons who would have taken another path. In addition, the use of graphene which has a linear dispersion makes it possible to transmit undistorted waves in order to transmit quantum information.
This guide could ultimately be integrated in the architecture of a quantum computer to transmit the electrons information (encoded in the spin, energy or moment of the electron). It will be more widely used to perform on the electron experiments currently made for photons, and thus advance the field of electronic optics.
* UMR CNRS, École Polytechnique, CEA