In the last few years, the great utility of exceptional points in sensing linear perturbations has been recognized. However, physical systems are inherently anharmonic and macroscopic physics is most accurately described by nonlinear models. Considering the multitude of semiclassical and quantum effects ensuing from nonlinear interactions, the sensing of anharmonicities is a prerequisite to the primed control of these effects. Here, we propose an expedient sensing scheme relevant to dissipatively coupled anti parity-time (anti-PT) symmetric systems and customized for the fine-grained estimation of anharmonic perturbations. The sensitivity to anharmonicities is derived from the coherence between two modes induced by a common vacuum. Owing to this coherence, the linear response acquires a pole on the real axis. We demonstrate how this singularity can be exploited for the enhanced sensing of very weak anhamonicities at low pumping rates. Our results are applicable to a wide class of systems, and we specifically illustrate the remarkable sensing capabilities in the context of a weakly anharmonic yttrium iron garnet sphere interacting with a cavity via a tapered fiber waveguide. A small change in the anharmonicity leads to a substantial change in the induced spin current.

中文翻译：

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通过耗散耦合的反PT对称系统中的相干性增强对弱非谐性的感知

在过去的几年中，人们已经认识到特殊点在感知线性扰动方面的巨大效用。但是，物理系统本质上是非调和的，而宏观物理可以用非线性模型最准确地描述。考虑到非线性相互作用产生的大量半经典效应和量子效应，对非谐波的感测是对这些效应进行预控制的前提。在这里，我们提出了一种与耗散耦合的反奇偶时间（anti-PT）对称系统相关的权宜的传感方案，并针对非谐扰动的细粒度估计进行了定制。对非谐性的敏感性是由共同真空引起的两个模式之间的相干性得出的。由于这种相干性，线性响应在实轴上获得一个极点。我们演示了如何在低抽速下利用这种奇异性增强对非常弱的失谐性的感知。我们的结果适用于各种各样的系统，并且在弱非谐钇铁石榴石球通过锥形光纤波导与腔相互作用的情况下，我们特别说明了非凡的感测能力。非谐波的微小变化会导致感应自旋电流发生实质性变化。