  We investigate coherent electron-switching transport in a double quantum
waveguide system in a perpendicular static or vanishing magnetic field. The
finite symmetric double waveguide is connected to two semi-infinite leads from
both ends. The double waveguide can be defined as two parallel finite quantum
wires or waveguides coupled via a window to facilitate coherent electron
inter-wire transport. By tuning the length of the coupling window, we observe
oscillations in the net charge current and a maximum electron conductance for
the energy levels of the two waveguides in resonance. The importance of the
mutual Coulomb interaction between the electrons and the influence of
two-electron states is clarified by comparing results with and without the
interaction. Even though the Coulomb interaction can lift two-electron states
out of the group of active transport states the length of the coupling window
can be tuned to locate two very distinct transport modes in the system in the
late transient regime before the onset of a steady state. A static external
magnetic field and quantum-dots formed by side gates (side quantum dots) can be
used to enhance the inter-waveguide transport which can serve to implement a
quantum logic device. The fact that the device can be operated in the transient
regime can be used to enhance its speed.
