  We present a way to manipulate an electron trapped in a layered quantum dot
based on near-threshold properties of one-body potentials. We show that
potentials with a simple global parameter allows the manipulation of the wave
function changing its spatial extent. This phenomenon seems to be fairly
general and could be implemented using current quantum-dot quantum wells
technologies and materials if a proper layered quantum dot is designed. The
layered quantum dot under consideration is similar to a quantum-dot quantum
well device, i.e. consists of a spherical core surrounded by successive layers
of different materials. The number of layers and the constituent material are
chosen to highlight the near-threshold properties.
  In particular we show that the near-threshold phenomena can be observed using
an effective mass approximation model that describes the layered quantum dot
which is consistent with actual experimental parameters.
