Adiabatic Shortcuts And Particle Layout Evolution In A Two-level System

Adiabat is an ideal physical process and needs a long time to complete due to existing in all kinds of slow changing physical processes.In order to accelerate the adiabatic evolution process and achieve energy transfer through adiabatic path in a short period of time,the adiabatic shortcut is appeared.Thus,in the two-level system,how to use adiabatic shortcut to speed up the adiabatic process and complete the fully transferred population in a short time become a hot issue of quantum physics.In this paper,the main research results are as follows:1.The research background and the development status of adiabatic shortcut as well as the influence factors of diabatic in quantum systems have been introduced.Usually,there are three method of adiabatic shortcut:transitionless quantum driving,Lewis-Riesenfeld invariant theory and rapid adiabatic process.In the two-level system,these methods are used to change of the Hamiltonian coupling and achieve the maximum transfer of population,the adiabatic evolution process has been completed.2.The physical mechanism of the complete population transfer process is studied when Rabi frequency is smaller by the method of CDF in two-level atomic system.Results show,the main role of adding a CDF is to modify the light field form of the Rabi frequency for the system,and such a quick pulse light field can make the eigenvalues of the system have two degenerate points which have the same energy and are nearest between them.Through such two energy degenerate points,the system can achieve two diabatic processes,where the second step is the inverse of the firstone,or the time reversal process,restoring the system to its original state eventually and achieving the super adiabatic evolution.3.It is a basic problem to study the population transfer process between the energy states by using the idea of non-Hermitian quantum adiabatic physics.In this paper,the diagonal elements of the Hamiltonian of the system are modified to have a complex variable.The imaginary part of the Hamiltonian diagonal elements in the non-Hermitian system corresponds to the gain or decay in the two-level system.Such a system is a typical non-Hermitian system,and the eigenvalues of the Hamiltonian are complex.In the non-Hermitian system,even if the coupling term is very small,the particle population can be transferred in a short time.