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arXiv 1205.6089quant-ph
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非热平衡稳态环境中的量子系统

Quantum systems in a stationary environment out of thermal equilibrium

Bruno Bellomo, Riccardo Messina, Didier Felbacq, Mauro Antezza

摘要:

讨论了当系统处于非热平衡的环境中时,基本量子系统的热化是如何被修正的。为了这个目的,我们提供了一个详细的调查的动力学的原子系统放置在靠近一个机构的任意几何形状和介电常数,其温度$T_M$是不同的周围的墙壁$T_W$。一个合适的主方程的一般情况下的$N$能级原子的推导,然后专门的情况下的两个和三个能级原子。过渡率和稳定状态明确表示为散射矩阵的身体的功能,并成为定性和定量的辐射在热平衡的情况下不同。在平衡之外,系统稳态取决于系统-身体距离、身体的几何形状以及所有这些参数与身体光学共振的相互作用。虽然二能级原子倾向于热态,但在存在三个原子能级的情况下,情况并非如此。这种特殊的行为可以被利用,例如,反转粒子数排序,并为量子系统的内部状态提供有效的冷却机制。最后,我们提供了数值研究和渐近表达式时,身体是一个有限厚度的平板。我们的预测可以是相关的一个广泛的实验配置类的热平衡涉及不同的物理实现的两个或三个级别的系统。

英文摘要:

We discuss how the thermalization of an elementary quantum system is modified when the system is placed in an environment out of thermal equilibrium. To this aim we provide a detailed investigation of the dynamics of an atomic system placed close to a body of arbitrary geometry and dielectric permittivity, whose temperature $T_M$ is different from that of the surrounding walls $T_W$. A suitable master equation for the general case of an $N$-level atom is first derived and then specialized to the cases of a two- and three-level atom. Transition rates and steady states are explicitly expressed as a function of the scattering matrices of the body and become both qualitatively and quantitatively different from the case of radiation at thermal equilibrium. Out of equilibrium, the system steady state depends on the system-body distance, on the geometry of the body and on the interplay of all such parameters with the body optical resonances. While a two-level atom tends toward a thermal state, this is not the case already in the presence of three atomic levels. This peculiar behavior can be exploited, for example, to invert the populations ordering and to provide an efficient cooling mechanism for the internal state of the quantum system. We finally provide numerical studies and asymptotic expressions when the body is a slab of finite thickness. Our predictions can be relevant for a wide class of experimental configurations out of thermal equilibrium involving different physical realizations of two or three-level systems.

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