论文标题

热能传输的量子相干控制:V模型作为案例研究

Quantum coherence-control of thermal energy transport: The V model as a case study

论文作者

Ivander, Felix, Anto-Sztrikacs, Nicholas, Segal, Dvira

论文摘要

在这里,我们研究了一个最小模型,即与两个热浴的三级V系统,并研究了量子相干在瞬态状态和非平衡稳态中的热传输中的作用。在我们的模型中,通过两个平行途径在浴缸之间交换了能量,这可以通过激发级别的非平稳级(能量分裂$δ$)和一个控制参数$α$进行区分,从而调整了其中一个臂的强度。使用Redfield形式的非量子量子主方程,我们成功地得出了量子相干的闭合形式表达式,并在稳态限制下以紧密退化激发水平的稳态极限。通过在我们的分析中包括三种成分:非平衡浴,水平的非平稳性以及途径的不对称性,我们表明,如果三个条件(三个条件)同时满足了三个浴场,则在稳态限制中产生量子相干并维持在稳态限制中: (ii)浴室诱导的途径不会破坏性干扰。 (iii)热速率不会与控制参数$α$混合以通过有效的局部平衡条件破坏干扰。我们发现当抑制热电流时,连贯性最大。另一方面,世俗的红场量子主方程显示在广泛的参数中失败。尽管我们主要关注稳态限制的分析结果,但数值模拟表明,连贯的瞬态行为与稳态极限进行了对比,这表明在这两个方案中,不同的机制在起作用。因此,增强瞬态相干的寿命或在稳态下的幅度需要控制和优化不同的物理参数。

Here, we study a minimal model, the three-level V system coupled to two heat baths, and investigate the role of quantum coherences in heat transport in both the transient regime and in the nonequilibrium steady-state. In our model, energy is exchanged between the baths through two parallel pathways, which can be made distinct through the nondegeneracy of excited levels (energy splitting $Δ$) and a control parameter $α$, which adjusts the strength of one of the arms. Using a nonsecular quantum master equation of Redfield form, we succeed in deriving closed-form expressions for the quantum coherences and the heat current in the steady state limit for closely degenerate excited levels. By including three ingredients in our analysis: nonequilibrium baths, nondegeneracy of levels, and asymmetry of pathways, we show that quantum coherences are generated and sustained in the V model in the steady-state limit if three conditions, conjoining thermal and coherent effects are simultaneously met: (i) The two baths are held at different temperatures. (ii) Bath-induced pathways do not interfere destructively. (iii) Thermal rates do not mingle with the control parameter $α$ to destroy interferences through an effective local equilibrium condition. We find that coherences are maximized when the heat current is suppressed. On the other hand, the secular Redfield quantum master equation is shown to fail in a broad range of parameters. Although we mainly focus on analytical results in the steady state limit, numerical simulations reveal that the transient behavior of coherences contrasts the steady-state limit, suggesting that different mechanisms are at play in these two regimes. Enhancing either the lifetime of transient coherences or their magnitude at steady state thus requires the control and optimization of different physical parameters.

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