Hysteresis-based Sensing enhanced by Nonlinear Exceptional-Points

Exceptional point degeneracies (EPDs) of non-Hermitian systems are points in parameter space where the eigenvalues and eigenvectors coalesce. The sublinear response of an external perturbation away from the EPD in parameter space has been proposed for hypersensitive sensing. However, in linear systems, it was found that fundamental and/or technical noise offsets the enhanced sensitivity in the proximity of the EPD. In our previous work, we developed a self-oscillating electronic dimer that is noise resilient by explicitly implementing nonlinearities. The presence a nonlinear EPD (NLEPD) separates two distinct dynamical regimes of oscillation quenching mechanisms – oscillation death (OD) and amplitude death (AD) – where the former is characterized by a spatially asymmetric steady-state with one stable mode and the latter is a spatially symmetric steady-state with two stable modes. We find that our platform exhibits two distinct sublinear responses depending on the type of voltage variation – detuning of resonant frequency in the OD regime or changes in coupling in the AD regime. We utilize both types of perturbations to demonstrate a hysteresis, which occurs due to the bistability in the AD regime, that we propose as a new observable for sensing. This protocol allows for experimental self-calibration of the NLEPD point, overcoming technical issues that have plagued linear experimental setups – indicating the promise of nonlinear systems for real-world sensing applications.