Remote Control Of The Evolution Speed Of Quantum State Dynamics

Quantum coherent states and quantum entanglement states are an important resource of quantum computation and quantum information processing,and also an important feature of the quantum world.Quantum entanglement can be used to accomplish tasks that the classical theoretical world cannot.With the development of quantum information technology,how to get more high speed quantum computing and information processing ability is the key of the current research problems,thus the concept of a quantum speed limit time has been generated by considering the distinguish from initial state to the final state to evaluate the required for the shortest time.Therefore,by using quantum speed limit time to study the quantum state of the open system to accelerate the evolution problem has caused wide attention of scholars both at domestic and foreign.This paper focuses on the two-level atomic system,and constructs a reasonable and feasible adjustable environment to realize the effective control of the evolution speed of the system quantum state.1.The influence of parameters of entangled coherent light field on the maximum evolution speed of quantum states is studied.Considering the two-mode entangled coherent light field,a mode of the light field is injected into the cavity and interacts with a two-level atom.According to the quantum electrodynamics theory of cavity,the evolution state of the atomic system is deduced.In view of the dynamic process from the initial state of an atomic system to the target evolution state,the concept of quantum speed limit time is used to characterize the maximum evolution speed of the quantum state of an atomic system.The maximum evolution speed in quantum state dynamics of atomic system is controlled by adjusting the coherent parameters of the two-mode entangled coherent light field.It is found that the coherent parameters of the light field interacting with the atom can have a significant influence on the maximum evolution speed of the quantum state of the atomic system under certain conditions.Moreover,when the interacting light field parameters cannot control the maximum evolution speed of the quantum state well,the quantum correlation between the two-mode entangled coherent light field can realize the remote control of the maximum evolution speed of quantum state of atomic system by the light field parameters that do not participate in the atom-light interaction.2.The effect of physical parameters in the lossy cavities on the quantum speed limit time of a qubit system is studied.In the actual evolution process,the system will inevitably be coupled to the surrounding environment,resulting in quantum dissipation.By considering two entangled light field and injecting a single mode light field into a lossy cavity containing a singletwo-level atom,we mainly explore how to accelerate the quantum state dynamics of an atomic system by adjusting relevant parameters by using the concept of quantum speed limit time.We obtain a meaningful conclusion: when the target state evolution is fixed,we can adjust the dissipation coefficient to realize the process of the evolution speed of the quantum state from no accelerating ability to the accelerating ability being improved.Dissipation coefficient is smaller the acceleration ability stronger.When the dissipation coefficient determined,we can also realize the maximum evolution speed of the quantum state from no speedup to speedup by considering the longer the actual evolution time.And on this basis by adjusting the initial correlation angle,we can continue to increase the acceleration of quantum state evolution within a certain range.When the parameters related to the light field cannot continue to increase the maximum evolution speed of the quantum state,in view of the wonderful entanglement of the entangled light fields,we can improve the maximum evolution speed of the quantum state dynamic process of the atomic system by increasing the number of entangled cavity fields.