Collective Excitation Control And Entanglement Based On Rydberg Dipole Blockade Effect

Rydberg atom are extremely attractive in quantum compute and quantum information due to their special properties such as large electric dipole moment and long radiation lifetime of atoms.In particular,the strong dipole-dipole interaction between Rydberg atom is the basis of the dipole blockade effect of Rydberg atom.The dipole blockade effect also provides a reliable platform for various new quantum tasks such as cryptography and quantum information processing.Moreover,quantum entanglement is produced based on the dipole blockade effect,which is a basic element of quantum physics.In this thesis,the dynamic behavior of superatom in a two-level system with time evolution is studied.At the same time,the preparation of the largest entanglement state between superatom is discussed in detail,and the interaction between three superatom is further discussed.The second chapter of the thesis mainly introduces the theories,concepts and important definitions closely related to this article.The specific research content is concentrated in the third and fourth chapters.In Chapter 3,we use Lindblad master equation to study the in-phase and anti-phase control of two superatom and the entanglement of collective states in a two-level system.By trapping two two-level superatom in two optical traps,based on the strict dipole blockade effect,the atomic ensemble can be transformed into two superatom,one of which is the control superatom and the other is the target superatom.First of all,the two superatom are prepared in the ground state.After a long time of evolution,the two superatom can oscillate in-phase,and then the maximum entanglement state between the superatom can be prepared.Furthermore,when the first superatom is in an excited state,the reverse dynamic evolution behavior of the two superatom can be realized.In particular,by changing the number of atoms in a superatom,the in-phase and anti-phase behavior of a single atom and a superatom can be controlled.In Chapter 4,we using the method of the chapter three,the dynamics of two superatom is extended to three superatom.The coherent dynamical evolution of three superatom in the same blockade region under different initial states is discussed,and the entanglement between superatom is measured.When the initial states of the superatom are all prepared in the ground state,it can be observed that the three superatom can achieve perfect in-phase dynamics evolution.Even if the superatom do not meet the equal conditions,the in-phase dynamics will not be affected.By continuing to change the initial state of the atom,the anti-phase dynamics between the first and second(first and third)superatom can be obtained.Similarly,the unequal number of atoms in superatom will not affect the reverse evolution.Furthermore,the maximum entanglement between superatom is not measured under in-phase and anti-phase evolution,but the initial state of superatom is prepared in the ground state when the system evolves to the W state when the excitation probability is maximum.In this paper,we use the superatom model,based on the strict dipole blockade effect.on the one hand to achieve the in-phase and anti-phase control of single atoms to superatom.on the other hand,we also prepare the maximum entanglement state between superatom.Regarding the dynamics of the three superatom,we can get the evolution of the system from the ground state to the W state under entanglement when the initial state of the superatom is prepared in the ground state.It not only proves the feasibility of using two-level many-body atoms to prepare many-body entanglement,but also helps people further understand the interaction mechanism between atoms in many-body system.