Dynamics of the qaanturn system Lhat 0msLsts d a cold atom in a moclulated standing wave of light is analyzed using the time-depmdmt variaticnal principle formulation based on squeezed coherent states. A group of ordinary differential equations describing evolutioa of two pairs of canonically conjugate variables(q(t),p(t):G(t),II(t)) are derived where G(t) and II(t) describe the quantum fluctuations of the system,It has been shown that a transition from the regular motion to the chaotic motion in G(t),II(t) phase space.Quantum system seems to be capable to show the classical-like chaotic structure.