  An electron floating on the liquid Helium is proposed to be trapped (by a
micro-electrode set below the liquid Helium) in a high finesse cavity. Two
lowest levels of the vertical motion of the electron acts as a two-level
"atom", which could resonantly interact with the THz cavity. In the Lamb-Dicke
regime, wherein the electron's in-plane activity region is much smaller than
the wavelength of the cavity mode, the famous Jaynes-Cummings model (JCM) could
be realized. By applying an additional external classical laser beam to the
electron, a driven JCM could also be implemented. With such a driven JCM
certain quantum states, e.g., coherent states and the Schrodinger cat states,
of the THz cavity field could be prepared by one-step evolution. The numerical
results show that, for the typical parameters of the cavity and electron on
liquid Helium, a strong coupling between the artificial atom and the THz cavity
could be obtained.
