Enhanced sensing of weak anharmonicities through coherences in dissipatively coupled anti-PT symmetric systems

TL;DR

This paper introduces a novel sensing method leveraging vacuum-induced coherences in dissipatively coupled anti-PT symmetric systems, enabling enhanced detection of weak anharmonicities without requiring gain.

Contribution

It proposes a new approach for sensing weak anharmonicities using coherence effects in anti-PT symmetric dissipative systems, applicable to systems like YIG spheres.

Findings

Vacuum-induced coherence enhances sensitivity to anharmonicities.

Higher drive powers create new coherence domains.

Significant change in spin current with small anharmonicity variations.

Abstract

In the last few years, the great utility of PT-symmetric systems in sensing small perturbations has been recognized. Here, we propose an alternate method relevant to dissipative systems, especially those coupled to the vacuum of the electromagnetic fields. In such systems, which typically show anti-PT symmetry and do not require the incorporation of gain, vacuum induces coherence between two modes. Owing to this coherence, the linear response acquires a pole on the real axis. We demonstrate how this coherence can be exploited for the enhanced sensing of very weak anhamonicities at low pumping rates. Higher drive powers ($\sim 0.1$ W), on the other hand, generate new domains of coherences. 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 (YIG) 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.