Enhanced quantum coherence of plasmonic resonances with a chiral exceptional point

Abstract Strong dissipation of plasmonic resonances is detrimental to quantum manipulation. In this work, we showcase the quantum coherence of plasmonic resonances can be significantly enhanced by integrating with photonic cavity operated at a chiral exceptional point (CEP), where the phase of light offers a new degree of freedom for flexibly manipulating quantum dynamics. The few-mode quantization theory is employed to demonstrate the advantages and related quantum-optics applications of the proposed hybrid cavity in both off- and on-resonance plasmon-photon coupling. For the former case, local density of states (LDOS) can evolve into sub-Lorentzian lineshape, with order-of-magnitude enhancement and linewidth narrowing compared to that without CEP. This results in the enhanced coherent light-matter interaction accompanied by reduced dissipation of polaritonic states. On resonance two mechanisms are responsible for significant improvement of quantum yield at CEP, by reducing plasmonic absorption through Fano interference and enhancing cavity radiation through superscattering. The latter allows achieving near-unity quantum yield in cryostat and enhancing room-temperature quantum yield by two orders of magnitude. Therefore, CEP-engineered plasmonic resonances can serve as a promising platform for exploring the quantum states control by virtue of the non-Hermiticity of open resonators and building high-performance quantum devices for sensing, spectroscopy, and quantum computing.