Wu Lian-Ao, Kurizki Gershon, Brumer Paul
Center for Quantum Information and Quantum Control and Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
Phys Rev Lett. 2009 Feb 27;102(8):080405. doi: 10.1103/PhysRevLett.102.080405.
Given a multilevel system coupled to a bath, we use a Feshbach P, Q partitioning technique to derive an exact trace-nonpreserving master equation for a subspace S_{i} of the system. The resultant equation properly treats the leakage effect from S_{i} into the remainder of the system space. Focusing on a second-order approximation, we show that a one-dimensional master equation is sufficient to study problems of quantum state storage and is a good approximation, or exact, for several analytical models. It allows a natural definition of a leakage function and its control and provides a general approach to study and control decoherence and leakage. Numerical calculations on an harmonic oscillator coupled to a room temperature harmonic bath show that the leakage can be suppressed by the pulse control technique without requiring ideal pulses.
对于一个与热库耦合的多能级系统，我们使用费什巴赫P、Q划分技术来推导该系统子空间(S_{i})的精确的非迹保持主方程。所得方程恰当地处理了从(S_{i})到系统空间其余部分的泄漏效应。聚焦于二阶近似，我们表明一维主方程足以研究量子态存储问题，并且对于几个解析模型是一个很好的近似或精确解。它允许自然地定义泄漏函数及其控制，并提供了一种研究和控制退相干与泄漏的通用方法。对耦合到室温简谐振子热库的简谐振子进行的数值计算表明，无需理想脉冲，通过脉冲控制技术就可以抑制泄漏。
