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arXiv 2403.04488quant-ph
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非平衡自旋玻色子模型的动力学:主方程基准及其有效性

Dynamics of the Non-equilibrium spin Boson Model: A Benchmark of master equations and their validity

Gerardo Suárez, Marcin Łobejko, Michał Horodecki

AI总结:

本文针对自旋玻色子模型,基准比较了非马尔可夫但完全正定的累积量主方程与精确解及其他主方程,发现其在弱至中等耦合和低温下更优,高温下优势消失,并利用SU(N)基简化了计算。

摘要:

近年来,人们高度关注开放量子系统的有效描述(如主方程)能否准确描述开放量子系统的动力学。一个特别的问题是,这些描述在长时间极限下能否提供正确的稳态。瞬态区域也备受关注。各种主方程(其中一些并非完全正定)对演化的描述已与精确解进行了基准比较(例如,参见 Hartmann 和 Strunz,Phys. Rev. A 101, 012103)。真实演化的一个重要特性是其非马尔可夫特征,而最简单的完全正定主方程无法捕捉这些特征。\n 在本文中,我们考虑一种非马尔可夫但完全正定的演化(称为精细弱耦合或累积量方程),用于具有过阻尼德鲁德-洛伦兹谱密度和任意耦合的自旋玻色子模型。我们将其与数值精确解以及其他主方程在不同耦合强度和温度下进行了基准比较。我们发现,在弱耦合区域(该方程预期有效的区域),累积量方程是更好的描述。对于所考虑的所有示例,在低温区域的中等和强耦合下,它表现出优越性。然而,在高温区域,其优势消失。这表明累积量方程是弱至中等耦合和低温下模拟的良好候选方案。我们通过使用 SU(N) 基中密度矩阵的表示,对累积量方程进行了简明表述,这大大促进了我们的计算。

英文摘要:

In recent years, there has been tremendous focus on identifying whether effective descriptions of open quantum systems such as master equations, can accurately describe the dynamics of open quantum systems. One particular question is whether they provide the correct steady state in the long time limit. Transient regime is also of interest. Description of evolution by various master equations - some of them being not complete positive - is benchmarked against exact solutions (see e.g. Hartmann and Strunz, Phys. Rev. A 101, 012103). An important property of true evolution is its non-Markovian features, which are not captured by the simplest completely positive master equations. In this paper we consider a non-Markovian, yet completely positive evolution (known as refined weak coupling or cumulant equation) for the Spin-Boson model with an Overdamped Drude-Lorentz spectral density and arbitrary coupling. We bench-marked it against numerically exact solution, as well as against other master equations, for different coupling strengths and temperatures. We find the cumulant to be a better description in the weak coupling regime where it is supposed to be valid. For the examples considered it shows superiority at moderate and strong couplings in the low-temperature regime for all examples considered. In the high-temperature regime however its advantage vanishes. This indicates that the cumulant equation is a good candidate for simulations at weak to moderate coupling and low temperature. Our calculations are greatly facilitated due to our concise formulation of the cumulant equation by means of representation of the density matrix in the SU(N) basis.

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