Four-wave-mixing-induced robust exceptional point in a single electronic resonator

Abstract

Exceptional points (EPs) offer significant promise for metrology via enhanced sensing, and electronic resonators have recently emerged as key platforms for EP generation due to their compactness and cost-effective components. However, an electronic resonator supports one eigenmode and thus struggles to adopt the optical platform's strategy for two-dimensional EP expansion, limiting robustness against fabrication flaws and environmental fluctuations. We introduce an approach to achieve robust EPs within a single electronic resonator. Specifically, by injecting a stabilized sinusoidal signal, the four-wave mixing mechanism inside the resonator generates a synthesized mode with the inherent mode, and these two modes form an anti-parity-time symmetry. This approach eliminates the physical inter-resonator coupling and reduces the number of resonators (the degree of freedom for EP generation), resulting in robust EP generation. Benefiting from the robust arrangement, a pronounced nonlinear feature leads to more than 40 branches of EP₂ degeneracy lifting (achieving more than 20-fold sensitivity enhancement relative to conventional EP sensors) and enables the first observation of chiral spectra as a unique EP degeneracy fingerprint. More critically, this approach offers a digitally controlled EP, offering real-time and continuous tuning of coupling strength. Benefiting from the tuning property, a 6-dB SNR improvement is achieved through stochastic resonance. This architecture facilitates a robust platform for EP-based sensing, unlocking opportunities to exploit EP functionalities.