We propose three schemes to engineer a circular state (superposition of the
harmonic oscillator coherent states on a circle in phase space) for the ce
ntre-of-mass motion of a trapped ion. We analyse the necessary duration of
each laser pulse for constructing such states, and calculate the probabilit
y of obtaining the subtle superposition. We also show that it is possible t
o engineer Fock number states as a result of the interference effects in ph
ase space of the coherent states superposition.