论文标题
一种直接计算降低密度矩阵的新方法
A new method for directly computing reduced density matrices
论文作者
论文摘要
我们演示了第一个基于原理和可行的方法的功能，该方法允许对开放量子系统的降低密度矩阵元素的扰动计算，而无需使用任何主方程。该方法基于非平衡量子场理论等技术，例如热场动力学，Schwinger-keldsyh形式主义和Feynman-Vernon影响功能。它不需要Markov近似，并且本质上是Lehmann-Szymanzik-Zimmermann类似的减少。为了说明这种方法，我们将真实的标量字段视为一个开放量子系统与包含另一个实际标量字段的环境相互作用的开放量子系统。我们提供了一个通用公式，该公式允许在动量的基础上为任何数量的粒子进行密度矩阵元素的扰动计算。最后，我们考虑了一个简单的玩具模型，并使用此公式来获取某些系统减少密度矩阵元素的表达式。
We demonstrate the power of a first principle-based and practicable method that allows for the perturbative computation of reduced density matrix elements of an open quantum system without making use of any master equations. The approach is based on techniques from non-equilibrium quantum field theory like thermo field dynamics, the Schwinger-Keldsyh formalism, and the Feynman-Vernon influence functional. It does not require the Markov approximation and is essentially a Lehmann-Szymanzik-Zimmermann-like reduction. In order to illustrate this method, we consider a real scalar field as an open quantum system interacting with an environment comprising another real scalar field. We give a general formula that allows for the perturbative computation of density matrix elements for any number of particles in a momentum basis. Finally, we consider a simple toy model and use this formula to obtain expressions for some of the system's reduced density matrix elements.
