  Quark deconfinement phase transition at finite temperature and density is
investigated in the frame of quantum mechanics. By solving the Schr\"odinger
equation for a heavy quark in a thermal mean field, we calculate the quark
probability distribution as a function of temperature and density. The confined
wave function in the vacuum expands outward rapidly when the temperature and
density are high enough. The obtained phase transition line agrees
qualitatively with the result of lattice QCD.
