由涨落调控的量子源对二能级系统的定向泵浦

中文摘要 AI 辅助

共振经典场相干地驱动二能级系统，在普通弛豫下产生饱和而非定向的粒子数转移。这里我们表明，当激发源作为量子子系统保留并随后被求迹掉时，方向性会显现。我们将源建模为单激发自由度，或等价地，一串与目标二能级系统交换耦合的二能级辅助量子比特。源的一阶矩产生通常的相干驱动，而其二阶矩产生向上和向下的耗散通道。对于数对角、完全激发的源，一阶矩消失，仅剩向上通道，导致目标的单调泵浦。相同的结构既可从精确碰撞图也可从涨落调控的二阶量子主方程得出。对于指数衰减的源关联，泵浦速率表现出由关联时间τ_c控制的洛伦兹失谐依赖，并伴随色散频移。在存在热弛豫的情况下，稳态激发态布居数可超过共振驱动的光学布洛赫极限（二分之一）。在涨落调控的主方程框架内，这种定向泵浦表现为一种驱动诱导的耗散贡献，其强度和光谱响应由τ_c控制。

英文摘要

A resonant classical field drives a two-level system coherently and, with ordinary relaxation, produces saturation rather than directional population transfer. Here we show that directionality emerges when the excitation source is retained as a quantum subsystem and subsequently traced out. We model the source as a single-excitation degree of freedom, or equivalently a stream of two-level ancillas, exchange-coupled to a target two-level system. The source first moment generates the usual coherent drive, while its second moments produce upward and downward dissipative channels. For a number-diagonal, fully excited source, the first moment vanishes and only the upward channel remains, yielding monotonic pumping of the target. The same structure follows from both an exact collision map and a fluctuation-regulated second-order quantum master equation. For exponentially decaying source correlations, the pumping rate shows a Lorentzian detuning dependence governed by the correlation time $τ_c$, accompanied by a dispersive frequency shift. In the presence of thermal relaxation, the steady-state excited-state population can exceed the resonantly driven optical-Bloch limit of one half. Within the fluctuation-regulated master equation, this directional pumping arises as a drive-induced dissipative contribution whose strength and spectral response are controlled by $τ_c$.

发表机构

• Indian Institute of Science Education and Research Kolkata（印度科学教育与研究学院加尔各答分校）

机构由 AI 辅助整理，请以论文原文为准。

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22 pages, 4 figures