Exceptional points (EPs) are the singularities of a non-Hermitian system where the eigenenergies and eigenstates simultaneously coalesce, a topological property that gives rise to a plethora of exotic phenomena. Probing the EPs and associated effects requires the system to go through the EPs. However, the ultrahigh sensitivity of an isolated EP to the external disturbances makes accessing the EPs difficult. To overcome this limit, many approaches have been presented to form the exceptional line/ring and surface. Here, we demonstrate that a quantum exceptional chamber, which is a three-dimensional collection of the EPs, can be constructed in the coupled plasmon-quantum dot (QD) systems by the nondipole effect of the QD. For an asymmetric QD adjacent to a plasmonic nanoparticle, it is found that the contributions of multipole transitions to the coupling strength can be larger than that of dipole transition. The orientation-dependent quantum interference between the dipole and multipole transitions can lead to controllable switch between the weak and strong coupling, and provides an extra degree of freedom to form a high-dimension EP space. Our approach provides a robust platform for accessing the quantum EPs and related applications.

中文翻译：

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由耦合到纳米等离子体谐振器的量子点的大非偶极效应引起的量子异常室

异常点 (EP) 是非厄米系统的奇点，其中本征能和本征态同时合并，这种拓扑性质会产生大量奇异现象。探测 EP 和相关效果需要系统通过 EP。然而，孤立的 EP 对外部干扰的超高灵敏度使得访问 EP 变得困难。为了克服这个限制，已经提出了许多方法来形成特殊的线/环和表面。在这里，我们证明了一个量子例外室，它是 EP 的三维集合，可以通过 QD 的非偶极子效应在耦合等离子体 - 量子点（QD）系统中构建。对于与等离子体纳米粒子相邻的不对称 QD，发现多极跃迁对耦合强度的贡献可以大于偶极跃迁的贡献。偶极子和多极子跃迁之间依赖于取向的量子干涉可以导致弱耦合和强耦合之间的可控切换，并为形成高维EP空间提供额外的自由度。我们的方法为访问量子 EP 和相关应用程序提供了一个强大的平台。