A scheme to produce closely spaced high-quality one-dimensional electronic channels is presented. It is based on standard nanolithography fabrication applied to a single, wide quantum well AlGaAs/GaAs heterostructure where the spatial separation of the wire modes is given by Coulomb repulsion. The lack of a composition-induced barrier in the double layer leads to electron mobility of 5x10(6) cm(2)/Vs in the starting double two-dimensional system. This in turn yields high-quality one-dimensional channels following nanolithography, as shown by our detailed analysis of the magnetotransport properties of the system. Variable coupling is achieved by split-gate polarization and external magnetic-field intensity and orientation. The relevance for the implementation of coherent nanodevices of this fabrication approach is discussed. (C) 2002 American Institute of Physics.