Preparation Of Quantum Steering Via Coherent And Incoherent Processes

As a new research field,the science of quantum information has arisen over the last three decades.Quantum correlations,important resources of quantum information,attract a large number of interest of researchers.Quantum correlations were first proposed by Einstein,Podolsky and Rosen in 1935.Until 2007,Wiseman and co-workers formalized quantum correlations strictly in mathematics and according to the strength of correlations,they were divided into three classes,namely,Bell nonlocality,EPR steering and quantum entanglement.Because of its inherent asymmetry,EPR steering has important applications in quantum security,which has attracted a large number of scholars’ attention.In the practical systems,the quantum properties of the systems will quickly transition to the classical properties due to decoherent effect,which is bad for the generation of quantum correlations.However,the dissipative processes caused by the environment can be translated into transition between dressed states in atomic coherent systems,in which it plays a positive role in the generation of quantum correlations due to the Bogoliubov modes decay to the vacuum state.The advantage of atomic coherent systems is robust against the spontaneous emission,and it has great practical value.Our work is as follows:Firstly,we research continuous variable one-way EPR steering via incoherent pump with quantum interference.This scheme is considered in three-level Λ atoms where the generation of EPR steering can be effectively controlled by the linear polarization angle of incoherent pump field and quantum interference.Because the dissipation caused by environment can modulate the population difference of dressed states to affect the quantum correlation,the generation of EPR steering can also be modulated by the pump rate of incoherent pump varying with the polarization angle.In addition to the strong anti-interference ability of the system,the easy control of polarization angle also provides a simple method to control the generation of EPR steering.Secondly,the modulation of the orbital angular momentum of the incident beam on the side-band squeezing and entanglement in the Laguerre-Gaussian cavity system is studied.It is found that the orbital angular momentum of the beam can affect the side-band squeezing of the cavity modes and the quantum correlation between the exciton of quantum well and the cavity modes in the cavity.Finally,we research collective-mode EPR steering in atomic coherent system.In this scheme,the atomic coherence of a four-level atomic system with two driving fields is discussed.In the dressed state representation,one of the single transition channels is used to couple the four cavity modes,and the quantum correlation of the four cavity modes is obtained according to the dynamic properties of the system.Under different parameters,chain EPR steering,oneto-two EPR steering,two-to-one EPR steering and two-to-two EPR steering are generated.