We report the observation of controlled electron tunnelling between tw
o closely spaced one-dimensional (1D) electron waveguides implemented
using a split-gate scheme on a high mobility AlGaAs/GaAs heterostructu
re. The 1D to 1D tunnelling current shows a distinct bumpy pattern whe
n the electronic subband population in the two waveguides is modulated
. These results are consistent with a picture in which tunnelling prim
arily occurs when the 1D subbands in both waveguides line up in energy
as expected from energy and momentum conservation rules.