Ensembles of alkali or noble-gas atoms at room temperature and above are widely applied in quantum optics and metrology owing to their long-lived spins. Their collective spin states maintain nonclassical nonlocal correlations, despite the atomic thermal motion in the bulk and at the boundaries. Here we present a stochastic, fully-quantum description of the effect of atomic diffusion in these systems. We employ the Bloch-Heisenberg-Langevin formalism to account for the quantum noise originating from diffusion and from various boundary conditions corresponding to typical wall coatings, thus modeling the dynamics of nonclassical spin states with spatial inter-atomic correlations. As examples, we apply the model to calculate spin noise spectroscopy, temporal relaxation of squeezed spin states, and the coherent coupling between two spin species in a hybrid system.

中文翻译：

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热气体中集体自旋态的量子动力学

室温或高于室温的碱或惰性气体原子团由于其自旋寿命长而被广泛应用于量子光学和计量学。尽管原子在主体内部和边界处发生了热运动，但它们的集体自旋状态仍保持非经典的非局部相关性。在这里，我们对这些系统中原子扩散的影响进行了随机的，全量子描述。我们采用Bloch-Heisenberg-Langevin形式主义来解释源自扩散和源自与典型壁涂层相对应的各种边界条件的量子噪声，从而通过空间原子间相关性对非经典自旋态的动力学进行建模。举例来说，我们将该模型用于计算自旋噪声光谱，压缩自旋态的时间弛豫，