Tunneling Behavior Of Ultracold Atoms In Optical Traps

In recent years it has been realized that ultracold atoms in an optical lattice become a hot spot for the study of quantum information processing. Optical lattice provides a well carrier for us to study the quantum dynamics, and the technique of laser cooling and mechanical manipulations of particles with lights is very mature.In this paper, we mainly research the tunneling properties of ultracold atoms in a simple, one-dimensional optical lattice system, which is produced by two counter-propagating laser beams by using the path-intergal method. In order to study the tunneling of ultracold atoms in a single and double optical trap, we approximated optical lattices potential using the effective two plus cubic potential and fourth potential well. The states in the well are unstable due to the tunneling. The energy of the states is complex, and the imaginary part is related to the decay rate. Through the calculations, we obtain the decay rate of the ground state in the single well. Then the temperature-dependent features of the decay rate are considered in order to include the contributions from all of energy levels of the atom in the well. Our calculations show that the transition in the high temperature is thermal activation and in the low temperature is quantum tunneling. The tunneling process is found to be a second order transition with the temperature decrease. Secondly, the level splitting,which is caused by tunneling into the adjacent well is calculated. Finally, the interplay between tunneling and level splitting is studied. The calculations show that the tunneling splitting can make the decay rate of the ground state accelerated. This provides a basis for us to research the movement of cold atoms in optical lattices.