By means of the full quantum theory,the conditions of generating a periodical quantum echo in the two-photon channel of a atom bit with arbitrary (pure or mixed) initial states was investigated,in coherent light field.Having studied the effects both the atom bit initial state and the surroundings parameter on its fidelity evolution,respectively,the parameter for control the periodical quantum echo of the atom bit was got and discuss its physical characters was discussed,that may be as a possible theoretical basis to the realization of a high fidelity output of quantum information.
By means of the full quantum theory,the conditions of generating a periodical quantum echo in the two-photon channel of a atom bit with arbitrary (pure or mixed) initial states was investigated,in coherent light field.Having studied the effects both the atom bit initial state and the surroundings parameter on its fidelity evolution,respectively,the parameter for control the periodical quantum echo of the atom bit was got and discuss its physical characters was discussed,that may be as a possible theoretical basis to the realization of a high fidelity output of quantum information.
In the rotating-wave approximation,the produce and control for periodic quantum echo of atom bit interacting with a two-mode coherent light field is investigated via intensity-dependent coupling multiphoton channel by means of the full quantum theory.The effects on the evolution of the fidelity of atom bit for both the distribution form and distribution range of the average photon number of the two-mode coherent light field,and the photon number k of absorbed(emitted) as the atoms transition are discussed by numerical calculations,respectively.The system parameter of preparation and control for periodic quantum echo of atomic bits are obtained.According to the entanglement theory,the relation of the fidelity of atom bit with atomic reduced entropy is analyzed.The results show that atom bitkeeps good coherence and fidelity,and will produce periodic quantum echo for the two photon process as k=1,by regulation average photon number of the light fields being symmetrical or asymmetrical distribution and its value in a certain range.For k≥2 multiphoton process,the atom bit is always in a maximally entangled with the two-mode coherent light field so that the atom bit is in a state of partial distortion without periodic quantum echo.It is shown that the physical nature of the periodic quantum echo produce is periodic disentangled between the atom bit and the light field.
In this paper,the evolution of the fidelity of atomic states is investigated via a light field intensity -dependent coupling multiphoton channel,the preparation and the control for atom periodic quantum echo is discussed,as well.Considering the effects on the evolution of the fidelity of the atomic states by atomic coherent distribution angle,average photon number of the field,and photon number k absorbed (emitted)as the atom transition,respectively,we obtain the system parameter of preparation and control the atom periodic quantum echo,show up its physical characters of a high-fidelity output of the atomic information.
By means of the full quantum theory,we investigate the fidelity of quantum informationin an arbitrary(pure and mixed) states of the two identical atoms system in highly detunedcavity QED,the influence of the initial state of systems and the degree of the atoms coupledon the fidelity of quantum information is discussed,and the physical properties of the fidelityevolution is revealed.It is showed that the fidelity of systems evolves periodic,the amplitudeof the fidelity evolution is modulated by the mixture of the atoms,and the evolution frequencyis controlled by the degree of atoms coupled.Choose a suitable initial state of the two-atomscoupled parameter and controlling the interaction time properlyone can get a high fidelityoutput,and emerge periodic quantum echo.
In this paper,the Tavis-Cummings(TC) model is generalized to simultaneously consider atomic motions and fields via intensity dependent coupling.Evolution of the fidelity of quantum states of entangled two-atom with motion interacting with light field via intensity-dependence coupling is investigated by means of the full quantum theory.The effects on the evolution of the fidelity of quantum states from the initial entanglement factor of the two-atom and the average photon number n-and field-mode structure parameter p of the field are researched by numerical calculations.The formation rule of quantum echoes of two-atoms is analyzed,and its physical essence is revealed.The results show that period quantum echo of the two-atom is always produced in the case of field-mode structure parameter p=1,independent of light intensity n-and the initial entanglement factor of the two-atom.Bell-state atoms can produce quantum echo with 2π/p cycle on the conditions of strongly coherent field,via changing the p of from 1 to any value less than 800.When p≥800,no matter what value of takes,the light field is a vacuum field,weakly coherent field or strong coherent field,the fidelity of quantum states of the two-atom is always 1,that is the first class Bell state-atoms is in the fidelity state continuously.But when the initial entanglement factor of two-atom is 3π/4,no matter how both values of n-,p are,the fidelity of quantum states of the two-atom maintains 1,namely the two-atom is in the fidelity state of the second class Bell-state continuously.The conclusions show that the extension model has good properties of periodic quantum echoes of two-atom,and provides the theoretical parameters and physical carrier for high fidelity output of entangled two-atoms information and experimental implementation of quantum information processing in the noise environment.
By means of numerical methods,the fidelity of the system of a fock state field interacting with the two two-level atoms have been studied.The effects of cavity-atoms detuning,photon number and manipulation of the atom on fidelity of the system are discussed.The results show that the information is undistorted completely in the initial moment in the absence of manipulation of the atom.Moreover the frequency of the oscillation,the peak and the period of fidelity of the system can be controlled by cavity-atoms detuning,photon number and manipulation of the atom.The Information is distorted in the initial moment in the presence of the manipulation of atom.Fidelity of the system can be controlled by the manipulation of the classical filed.
In this paper, the Tavis-Cummings model is generalized to simultaneously consider the atomic motion and the field via intensity dependent coupling. Under the conditions of vacuum field, weakly and strongly coherent field, the entanglement evolution properties of two-atom-field and two-atom-two-atom are investigated using atomic reduced entropy and concurrence, respectively. According to evolution characteristics above, we prepare the W-class states of two-atom-field, two-atom Bell state, fidelity state of Bell-state atoms, single-photon state, two-photon state and stable number-states of field by selecting the interaction time of the two-atom-field, selecting the entanglement factor of the two-atom, regulating the field-mode structure parameter, controlling the probability amplitude of pure state of the system and selective measurement. The manipulation of two-atom Bell state sudden generation and its maintenance in a limited time, the formation of periodic quantum echo of Bell-state atoms and the continuous fidelity of Bell-state atomic information are achieved. The results show that the system has a powerful function of quantum information, and provide the physical carrier and theoretical parameters for experimental implementation of quantum information processing.