A spin (qubit) is in contact with a bosonic reservoir. The state of the reservoir contains a parameter $\varepsilon$ interpolating between quantum and classical reservoir features. We derive the explicit expression for the time-dependent reduced spin density matrix, valid for all values of $\varepsilon$ and for energy conserving interactions. We study decoherence and markovianity properties. Our main finding is that the spin decoherence is enhanced (full decoherence) when the spin is coupled to quantum reservoir states while it is dampened (partial decoherence) when coupled to classical reservoir states. The markovianity properties depend in a subtle way on the classicality parameter $\varepsilon$ and on the finer details of the spin-reservoir interaction. We further examine scattering and periodicity properties for energy exchange interactions.

中文翻译：

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耦合到储层的自旋的准经典极限


自旋 （qubit） 与玻色子储层接触。储层的状态包含一个参数 $\varepsilon$，用于在量子和经典储层特征之间进行插值。我们推导出了瞬态降阶自旋密度矩阵的显式表达式，该矩阵对 $\varepsilon$ 的所有值和能量守恒相互作用都有效。我们研究退相干性和马尔可维特性。我们的主要发现是，当自旋与量子储层态耦合时，自旋退相干性增强（完全退相干），而当自旋与经典储层态耦合时，自旋退相干性会减弱（部分退相干）。马尔可夫性性质以一种微妙的方式取决于经典参数 $\varepsilon$ 和自旋-储层相互作用的更精细细节。我们进一步研究了能量交换相互作用的散射和周期性特性。