  We propose a nanodevice based on a typical planar semiconductor
heterostructure with lateral confinement potential created by voltages applied
to local electrodes. We show how to obtain near parabolical confinement along
the nanodevice, and how to use coherent states of the harmonic oscillator for
spatial separation of electron densities corresponding to opposite spin
directions. In such a way, an entangled state of Schr\"odinger's cat type is
created. We performed simulations of a realistic nanodevice model by numerical
solving the time-dependent Schr\"odinger's equation together with simultaneous
tracking of the controllable confinement potential via solution of the
Poisson's equation at every time step.
