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arXiv quant-ph/9805027quant-ph
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腔QED中随机薛定谔方程的物理解释

Physical interpretation of stochastic Schroedinger equations in cavity QED

Tarso B. L. Kist, M. Orszag, T. A. Brun, L. Davidovich

备注：
12 pages RevTeX 3.0 + 6 figures (GIF format; for higher-resolution postscript images or hardcopies contact the authors.) Submitted to Phys. Rev. A
发表信息：
J. Optics B 1, 251-263 (1999)
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摘要：

我们提出了物理解释的随机方法，最近已经发展到描述的量子系统与水库相互作用的演变。相对于通常的约化密度算子方法，这是指合奏平均，这些方法处理的动力学的单一实现，并涉及随机薛定谔方程的解决方案。这些程序已被证明是完全等效的主方程的方法时，合奏平均采取了许多实现。我们表明，这些技术不仅是方便的耗散系统的数学工具，但实际上可能对应于具体的物理过程，对于任何温度的水库。我们考虑腔中的电磁场模与二能级或三能级原子束的相互作用，场模扮演小系统的角色，原子束代表有限温度下的水库，它们之间的相互作用由Jaynes-Cummings模型给出。我们表明，场态的演化，在连续监测的原子离开腔的状态下，可以描述的Monte Carlo波函数（量子跳跃）方法或随机薛定谔方程，取决于系统配置。我们还表明，Monte Carlo波函数方法导致，有限的温度下，本地化到跳跃Fock状态，而扩散方程方法导致本地化到扩散的平均光子数的状态，这对于足够小的温度是接近轻度压缩状态。

英文摘要：

We propose physical interpretations for stochastic methods which have been developed recently to describe the evolution of a quantum system interacting with a reservoir. As opposed to the usual reduced density operator approach, which refers to ensemble averages, these methods deal with the dynamics of single realizations, and involve the solution of stochastic Schrödinger equations. These procedures have been shown to be completely equivalent to the master equation approach when ensemble averages are taken over many realizations. We show that these techniques are not only convenient mathematical tools for dissipative systems, but may actually correspond to concrete physical processes, for any temperature of the reservoir. We consider a mode of the electromagnetic field in a cavity interacting with a beam of two- or three-level atoms, the field mode playing the role of a small system and the atomic beam standing for a reservoir at finite temperature, the interaction between them being given by the Jaynes-Cummings model. We show that the evolution of the field states, under continuous monitoring of the state of the atoms which leave the cavity, can be described in terms of either the Monte Carlo Wave-Function (quantum jump) method or a stochastic Schrödinger equation, depending on the system configuration. We also show that the Monte Carlo Wave-Function approach leads, for finite temperatures, to localization into jumping Fock states, while the diffusion equation method leads to localization into states with a diffusing average photon number, which for sufficiently small temperatures are close approximations to mildly squeezed states.

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