| Quantum information science involves a number of disciplines,such as communication,physics,computer,mathematics,etc.,is a new interdisciplinary,that is,physics and information science cross and integration.The basic principle of quantum mechanics is the foundation of quantum information science.Quantum information processing technology has certain advantages,in the following areas to break through the limitations of traditional information: such as information security,computing speed,information capacity.Quantum information processing technology has become one of the hotspots of information technology processing,attracting more and more domestic and foreign scholars attention,and provide a new method for the future development of information science,which has very important application value and scientific significance.This paper mainly discusses the following three aspects,and obtains some valuable conclusions:In chapter 1,the evolution of the two-level atomic system in the excited state of the initial state is studied in detail.The influence of the structural parameters of the dynamic and static environment on the evolution of the excited atomic system is studied.In the static no modulation ideal photonic band-gap model,with the increase of the half width,the energy dissipation to the cavity faster,the atomic system to lose coherence faster.As the center resonant frequency increases,there will be suppression attenuation.In the dynamic modulation,the modulation form of the ideal photonic band-gap environment is taken as:rectangular single pulse,rectangular periodic pulse and slow continuous modulation.On this basis,to discuss the library environment dynamic modulation of the different forms of atomic population evolution of the impact,respectively.The center resonant frequency of the library is modulated by the dynamic environment,and in any form of dynamic modulation,the attenuation suppression is reflected in the evolution of the atomic system.Due to the periodic alternation of the modulation and the non-modulation time,so that the atoms are affected by different environments,which makes the idea of using the environmental changes to modulate the coherent evolution of the atomic system.Comparison of four environmental models: single Lorentz,ideal photon band-gap,double Lorentz and square Lorentz on the evolution of excited state atoms.Static no modulation,the square Lorentz model library is compared with the other three kinds of environmental library,the atomic energy on the number of population oscillation the fastest,the atomic system to lose coherence speed and energy dissipation speed to the cavity the slowest.The time of atomic attenuation to ground state in a single Lorentz model library is shorter than that of the other three environmental pools.In the dynamic modulation,by comparing the photonic band-gap model with the single Lorentz model library found: the atomic decay to the ground state of the time is longer,the energy dissipation to the cavity faster,the atomic system is less coherent slower.In the photon crystal,the evolution process of the atomic population on the upper level in the static modulation is also discussed.By Changing the relative position of the atomic on the upper level and the band gap edge to affect the atomic population on the upper level with the evolution process.With the change of the relative position,that is,the energy level on the atom gradually moves from the band-gap band,the suppression spontaneous emission of the atoms gradually weakens,so that the atomic population on upper energy level of stable values become smaller and smaller,and finally zero.This spontaneous emission of atoms in the form of non-exponential attenuation,and for the general free space is an exponential form of attenuation,attenuation in different forms.In chapter 2,a new type of two-dimensional function photonic crystal is proposed,that is the dielectric constants of medium column are the functions of space coordinates,which is different from the conventional photonic crystal with a constant refractive index of the dielectric column.The new two-dimensional function photonic crystal can be prepared by photorefractive nonlinear optical effect or electro-optic effect.Its band gap structure is flexible,and it can be used for many times.Because the function photonic crystal reduces the symmetry of photonic crystal,which is more likely to form semi-Dirac points than conventional photonic crystal.We use the plane wave expansion method to deduce the characteristic equations for the TE and TM wave.The Fourier transform of the dielectric constant function form of the two-dimensional function photonic crystal is carried out.It is more complicated than in conventional two-dimensional photonic crystal.However,when the dielectric constant of the two-dimensional function photonic crystal dielectric column is taken as a constant,it is consistent with the Fourier transform of two-dimensional conventional photonic crystal,the two-dimensional conventional photonic crystal is a special case of the two-dimensional function photonic crystal.In the numerical analysis,the band gap structure of TE and TM wave of triangular lattice two-dimensional function photonic crystal is studied.By adjusting some parameters of the dielectric constant function form,it is found that the band gap number,position,width,absolute band gaps and semi-Dirac point of the two-dimensional function photonic crystal are changed,that is,the band gap structure is tunable.The band gap structure?defect mode and defect mode eigenfield distribution in square lattice two-dimensional function photonic crystal with vacancy type point defect are further studied.The study on the band gap structure of two-dimensional function photonic crystals provides new conditions for the controllability of the photonic crystal thermal reservoir,which can be used to facilitate the quantum control of the atoms in it.At the same time,it provides the scheme and theoretical basis for the design of two-dimensional photonic crystal optical devices.In chapter 3,we used the J-C model to study the quantum entanglement with time evolution law of atoms and light fields in the case of multiphoton transitions in linear and nonlinear media,and researched the effect of the transition photon number,the initial state parameter,the quantum discord,the initial photon number and the nonlinear coefficient on entanglement degrees.It is found that,with the number of transition photons or the number of initial photons increases,the evolution of entanglement degrees with time oscillations increase,and the number of entanglement increases to the maximum entanglement in the linear medium.When the initial state parameter is 76.01c(28),the initial state of atom and light field is close to maximum entanglement.The entanglement is close to the maximum entanglement state at any time,especially the transition photon number is large,the entangled state can be stable close to the maximum entanglement state,i.e.the more number of transitional photons,the more stable the quantum entangled state is in the maximum entanglement state.So the multi-photon transition in this case is very beneficial to quantum communication.In the nonlinear Kerr medium,there exists a nonlinear term in the J-C model.It is found that when the transition photon number N(28)2,the periodic oscillation of the entanglement evolution curve becomes slower,and keep the time of entanglement degrees near 1 is longer.When the nonlinear term coefficient increases,the transition photon number N(28)2,the entanglement keep the time of entanglement near 1 is longer obviously.These conclusions have important theoretical implications for fields such as quantum optics and quantum communication. |
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