量子光学中的非经典态

NON-CLASSICAL STATES IN THE QUANTUM OPTICS

本文扼要地介绍了光子数态、热光场态、相干态、压缩态、相位态和中间态等。重点是介绍它们的物理性质。例如，指出相干态在谐振子座标表象中的表示就是带电谐振子在均匀电场中的基态波函数；它的时间演化波包的概率密度分布，形状不随时间变但中心位置随时间作周期振荡。文中对相干态和压缩态等提供了也许是一点新的看法：将相干态、压缩真空态、压缩相干态和相干压缩态等看作是一准玻色子的基态或相干态。而实现的手段可以是原来的幺正算符也可以是投影算符。这样的好处是：（１）对相干态和压缩态间的联系有更深的认识；（２）便于计算和进一步展开等等。文中还对各个态的压缩性、统计性等作了介绍，有的还用图表等演示了它们的非类经典特性。最后，文中还介绍了准概率分布函数。

In the paper we have introdued the non-classical states in quantum optics: photon number states, coherent states, squeezed states, phase states and intermediate states etc., especially their physical properties. For examples, in the coordinate representation of harmonic oscillator, Glauber's coherent state namely is the ground state wave function ψ o(q) of the electrified harmonic oscillator, and the center of the probability distribution |ψ o(q,t)| 2 is periodically variant with time, but invariant in form of |ψ o(q,t)| 2. We have also shown that Glauber's coherent state and squeezed state can be considered ground states of new boson, and squeezed coherent state & coherent squeezed state can be considered coherent state of new bosons. New bosons can be obtained by original unitary transformation or vacuum projector. The superior points of such consideration are: (1) deepening cognition of the relations between coherent state and squeezed state; (2) easy to calulate and to develop. With the help of graph & chart, we have disussed the non-classical ppeerties of the above-menioned states: squeezability、statistics etc.. Finally, we have also introduced quasi-possibility distribution functions、phase-space techniques and their aplications, and given some instances.