Noise-assisted sensing via stochastic resonance near driven-dissipative nonlinear higher-order exceptional points

Exceptional points (EP_S) can enhance sensitivity for weak signal detection, but noise typically degrades their performance. Here, contrary to this conventional wisdom, we theoretically introduce and experimentally demonstrate a noise-assisted sensing paradigm leveraging stochastic resonances near a driven-dissipative nonlinear fourth-order exceptional point (EP₄). Using a minimal two-site model with asymmetric dissipation and single-site driving, we realize an EP₄ exhibiting fourfold degeneracy in steady-state eigenamplitudes under fixed-frequency driving. Crucially, this EP₄ coexists with third-order EP_S and second-order exceptional lines, partitioning a two-parameter space into mono-, bi-, and tristable regions. We demonstrate that noise induces bi- and multistable stochastic resonances, synergizing with the quartic-root dispersion around EP₄ to dramatically amplify weak signals and enhance signal-to-noise ratios. Experimental validation with nonlinear electrical circuits confirms these predictions. Our work establishes driven-dissipative nonlinear higher-order EP_S with eigenamplitude degeneracy as a potent platform for noise-enhanced sensing, harnessing nonlinear multistability and EP physics to transcend conventional noise limitations.