运用理想光子禁带模型实现对激发态原子系统演化的调控

Control of evolutionary atomic system of excited atom by using ideal photonic band-gap model

通过调节动静态理想光子禁带模型库的结构参数,研究了初态处于激发态的两能级原子系统的演化.在静态无调制下研究理想光子禁带模型库环境的半宽度、中心谐振频率及比重对原子布居数演化的影响.在理想光子禁带库环境的中心共振频率受动态调制下,其调制形式分别取为:矩形单次脉冲、矩形周期性脉冲和缓变连续周期.在此基础上讨论动态调制形式的不同对原子布居数演化的影响.无论怎样的动态调制形式,衰减抑制在原子系统的演化过程还是有较明显的体现.这样就使得利用环境变化对原子布居数和原子系统相干性演化调制的想法得以实现.

The evolution of two-level atomic system, in which the initial state is excited state, is investigated by ad3ustmg the structural parameters of the dynamic and static ideal photonic band-gap environment reservoir. In a static state （no modulation）, we study the effects of half width, center resonant frequency, and specific gravity on the evolution of energy level population. The results show that when the half width or the specific gravity decreases, in the atomic system there happens decoherence, and the energy dissipation to the outside becomes slower. When the center resonant frequency increases, there exists no resonance between the library central resonant frequency and the atom transition frequency, then the attenuation suppression effect occurs, and the time of atomic attenuation to ground state is longer. An actual quantum system is not isolated, so it is inevitable that it interacts with its ambient environment. Owing to the influence of environment, in the system there appears an irreversible quantum decoherence phenomenon. Therefore, how to effectively suppress the decoherence of quantum system becomes an important problem in quantum information science. Linington and Garraway （2008 Phys. Rev. A 77 033831） pointed out that the evolution process of a two- level atom quantum state can be manipulated by a dynamic dissipative environment. So, we use the dynamic cavity environment to control the evolution of spontaneous emission from an excited two-level atom. The dynamic modulation form for the center resonant frequency of the ideal photonic band-gap environment reservoir includes the rectangular single pulse, rectangular periodic pulse, and slow continuous period. Owing to the periodic modulation, the atoms are affected by different environments. On this basis, the influence of dynamic modulation form on the atomic population evolution is discussed. It is found that no matter what form the dynamic modulation is in, the attenuation inhibition in the evolution of atomic system is evident. These conclusions make the idea of using the environmental change to modulate the coherent evolution of atomic system become true.