Dissipative Dynamics Of Cold Atoms In An Optical Lattice

The cold atomic gas is a kind of electrically neutral thin gas with a temperature close to absolute zero.With the development of experimental technology,cold atom physics has gradually become a hot research field.Atoms will exhibit many novel and interesting quantum properties at very low temperature,such as Bose-Einstein Condensates(BEC),nonlinear quantum tunneling and superfluid-Mott insulation quantum phase transitions,etc.The cold atomic system has good adjustability and is an excellent platform for quantum simulation.As a pure and controllable experimental platform,the optical lattice has many unique advantages.Its lattice constant,potential well depth can be precisely controlled by adjusting the laser intensity,polarization and frequency,etc.In 2005,ultracold atomic gas was successfully put into the optical lattice for the first time,which made it possible to simulate the motion of electrons in the periodic lattice by using atoms.As an open system,cold atoms in an optical lattice also interact with the environment and there will also be a dissipation effect.However,recent experiments have shown that the controlled dissipation can be a beneficial tool for controlling quantum systems.Therefore,this paper mainly studies the influence of distance-selective dissipation and external driving on the dynamics of cold atoms in an optical lattice.Through numerical simulations,the influence laws of distance-selective dissipation and other factors on the transport of atoms and the methods to improve the transport efficiency of atoms in an optical lattice were found,so as to control the distribution of cold atoms in an optical lattice.The main works are as follows,First of all,the Markovian master equation is used to establish a mathematical model for describing the dynamics of cold atoms in a one-dimensional driven optical lattice.Then the mean-field approximation method is used to simplify the cold atomic system and the differential equations satisfied by the mean of physical quantity of the system are derived.Next,the fourth-order classical Runge-Kutta method is used to numerically solve these differential equations,in order to study the effects of distance-selective dissipation,external driving and atomic interaction on the dynamics of system.Through numerical simulations,we find that the localization and transport efficiency of atoms in an optical lattice can be improved by increasing the distance-selective dissipation or the interaction between atoms while the propagation speed of atoms will decrease.Secondly,the augment of external driving will reduce the localization of atoms in the transport process and destroy the periodic transport process of cold atoms.Last but not least,when the external driving varying with time is applied to the boundary of the optical lattice,the localization of atoms in the transport process can be improved and a highly localized periodic transport form can be obtained by adjusting the frequency,direction and intensity of the external driving.In summary,we can improve the localization and transport efficiency of atoms in the optical lattice and obtain the localized periodic transport form by adjusting the distance-selective dissipation rate,external driving deviation and the strength of the interaction between atoms,etc.,so as to control the distribution of cold atoms in an optical lattice.