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arXiv 2204.00643quant-phcond-mat.stat-mech
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由与环境有限强度耦合引起的哈密顿量修正

Corrections to the Hamiltonian induced by finite-strength coupling to the environment

Marcin Łobejko, Marek Winczewski, Gerardo Suárez, Robert Alicki, Michał Horodecki

AI总结:

本文针对量子系统与环境有限强度耦合,解析推导了兰姆位移、稳态和平均力三类哈密顿量二阶修正的通用公式,并应用于戴维斯、布洛赫-雷德菲尔德和累积量方程,以自旋-玻色子模型为例验证。

摘要:

如果一个量子系统与环境相互作用,那么哈密顿量会获得一个称为兰姆位移项的修正。还有另外两种与稳态相关的哈密顿量修正。即,稳态在首次近似下是关于原始哈密顿量的吉布斯态。然而,如果我们有有限耦合,那么真实的稳态将不同,将其视为某个有效哈密顿量的吉布斯态,可以提取出一个修正,称为“稳态”修正。或者,可以采取静态观点,考虑总平衡态的约化态,即系统加浴的吉布斯态。提取的哈密顿量修正称为“平均力”修正。本文提出了关于上述三种类型的二阶(在耦合强度上)修正的几个解析结果。我们不再关注稳态,而是关注由主方程的刘维尔算子湮灭的态,将其标记为“准稳态”。具体来说,我们推导了平均力修正以及一般类主方程的准稳态和兰姆位移修正的通用公式。此外,对于戴维斯、布洛赫-雷德菲尔德和累积量方程(精细弱耦合),获得了具体的修正公式。特别是,累积量方程作为刘维尔算子的案例研究,具有非平凡的四阶生成元。该生成元是计算对角准稳态修正的基础。我们以自旋-玻色子模型为例,除了使用我们的修正公式外,还考虑了来自反应坐标方法的平均力修正。

英文摘要:

If a quantum system interacts with the environment, then the Hamiltonian acquires a correction known as the Lamb-shift term. There are two other corrections to the Hamiltonian, related to the stationary state. Namely, the stationary state is to first approximation a Gibbs state with respect to original Hamiltonian. However, if we have finite coupling, then the true stationary state will be different, and regarding it as a Gibbs state to some effective Hamiltonian, one can extract a correction, which is called "steady-state" correction. Alternatively, one can take a static point of view, and consider the reduced state of total equilibrium state, i.e., system plus bath Gibbs state. The extracted Hamiltonian correction is called the "mean-force" correction. This paper presents several analytical results on second-order corrections (in coupling strength) of the three types mentioned above. Instead of the steady state, we focus on a state annihilated by the Liouvillian of the master equation, labeling it as the "quasi-steady state." Specifically, we derive a general formula for the mean-force correction as well as the quasi-steady state and Lamb-shift correction for a general class of master equations. Furthermore, specific formulas for corrections are obtained for the Davies, Bloch-Redfield, and cumulant equation (refined weak coupling). In particular, the cumulant equation serves as a case study of the Liouvillian, featuring a nontrivial fourth-order generator. This generator forms the basis for calculating the diagonal quasi-steady-state correction. We consider spin-boson model as an example, and in addition to using our formulas for corrections, we consider mean-force correction from the reaction-coordinate approach.

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