Coulomb blockade directional coupler

A tunable directional coupler based on Coulomb blockade effect is presented. Two electron waveguides are coupled by a quantum dot to an injector waveguide. Electron confinement is obtained by surface Schottky gates on a single GaAs/AlGaAs heterojunction. Magneto-electrical measurements down to 350mK are presented and large transconductance oscillations are reported on both outputs up to 4.2K. Experimental results are interpreted in terms of Coulomb blockade effect and the relevance of the present design strategy for the implementation of an electronic multiplexer is underlined.